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 OF ILLINOIS 
 
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UNIVERSITY OF ILLINOIS, 
 
 Agricultural Experiment Station. 
 
 URBANA, MARCH, 1897. 
 
 BULLETIN No. 47. 
 
 *BROOM-CORN SMUT. 
 
 RELATIONSHIP. 
 
 Related plants. Broom-corn is placed by botanists in the 
 genus Andropogon (Sorghum), one of the prominent genera of 
 the grass family. Closely related to this plant are a number of 
 other cultivated forms commonly known as sorghum, durra, Kafir 
 corn, Jerusalem corn, etc. These are considered by Hackel as 
 descended from a common ancestor and are therefore placed by 
 him as varieties under the species Andropogon Sorghum, of which 
 broom-corn is designated as Andropogon Sorghum var. technicus. 
 In different parts of the world, usually in the warmer regions, cer- 
 tain of these varieties have assumed considerable importance ; 
 especially during the last few years all of them have been more 
 largely cultivated in the United States and seem to merit this 
 increased attention. Any fungus or insect found at work on 
 them, therefore, may be considered of direct economic importance, 
 especially when serious injury is inflicted. 
 
 Related smuts. It is the purpose of this article to discuss at 
 length one of the fungous troubles of this group of plants a fungus 
 that is commonly designated as smut. As there are several species 
 that have been found on one or another of these plants, it may be 
 well to consider briefly all of the smuts before proceeding to the 
 
 *For those who may wish merely to get from this bulletin the practical method ot 
 preventing broom-corn smut, there has been prepared at the end, under " Prevention of 
 broom-corn smut," directions for the use of hot water in the treatment of broom-corn 
 seed. Also under " Summary," immediately preceding the above, are given briefly some 
 of the chief points that the bulletin presents. The writer wishes to acknowledge indebt- 
 edness and return thanks to the several botanists and to the growers and dealers in 
 broom-corn who have conferred such favors as the loan of specimens, references to liter- 
 ature, information concerning the injury and loss caused by the smut, etc. 373 
 
374 BULLETIN NO. 47. {March, 
 
 discussion of this particular one. From Cairo, Egypt, there has 
 been reported a smut in the flower parts of a variety of Andropogon 
 grown there. In this the spores adhere in small round balls, and 
 so the fungus is placed in the genus Sorosporium (Sorosporinm 
 Ehrcnbergii}, although originally the specimen was incorrectly 
 referred to a species of Ustilago (Ustilago Reiliana*}. So far it 
 seems to have been collected from that locality only. On the 
 same plant from central Asia another smut has been reported, 
 which by its discoverer, Sorokine, was described as a type of a 
 new genus, Endothlaspis ; but later it has been placed by De-Toni 
 doubtfully in the genus Cintractia (Cintractia Sorghi}. Tracy and 
 Earle report a single specimen of this from Mississippi, collected 
 in 1888. An examination of this specimen, however, shows that its 
 spores are larger than those of Cintractia Sorghi, as described by 
 De-Toni, and it corresponds so closely with Ustilago Reiliana that 
 it seems proper to consider it as belonging to that species. There 
 are three smuts apparently of the Ustilago type that have been 
 found on one or another of these varieties. The most conspicuous 
 is head smut (Ustilago Reiliana'), which turns the whole panicle 
 into a smutty mass. This is more common than the above, being 
 reported from Africa, Europe, and from two or three places in the 
 United States. The second one ( Ustilago cruenta) occurs in less 
 conspicuous outbreaks on the rays of the panicle, occasionally on 
 the stem itself, and in the flower parts. While a common form in 
 certain parts of Europe, this smut has not yet been reported in this 
 country. The third form ( Ustilago Sorghi) is quite similar to the 
 second but limits its attacks to the young inner flower parts, pro- 
 ducing a seed-like body filled with its spores. 
 
 Identity of broom-corn smut. A comparison of the specimens 
 of smuts collected on the sorghum-like plants in Kansas, Illinois, 
 New Jersey, and Wisconsin with European specimens of the above 
 Ustilagos leads to the conclusion that the smuts so far collected in 
 this country, when limited to the reproductive parts of the flower, 
 belong to the species Ustilago Sorghi. In fact this is the species 
 to which they have always been referred. Ustilago cruenta and 
 Ustilago Sorghi, however, are very closely related. The chief dif- 
 ferences between them that can be gathered from an examination 
 of descriptions and specimens are that the former may occur on 
 any part of the panicle or even on the stem, while the latter is 
 confined to the flower; that the former has spores that average 
 larger and are more variable in size and shape than the latter; that 
 the individual spores of the former are more apt to have a reddish 
 tint while the latter usually have a distinct olive tint. 
 
 * See de Thiimen Mycotheca universalis, No. 725. 
 
1897.} BROOM-CORN SMUT. 375 
 
 The reason for doubting the identity of our specimens was 
 caused by the description of the life history 1 of Ustilago cruenta as 
 given by Brefeld, especially the germination, 2 which seems to 
 agree very closely with what we have learned concerning the smut 
 on broom-corn, and also by the statement made by him that 
 Ustilago Sorglifi did not germinate in water, which seems to be a 
 very characteristic thing with the smut with which we have dealt. 
 It is barely possible that the Ustilago with which his chief investi- 
 gations were carried on might be considered by some botanists as 
 Ustilago Sorghi, instead of Ustilago cruenta, as they were with a 
 smut that was entirely confined to the inflorescence. But certainly 
 the evidence as a whole justifies the conclusion that our American 
 specimens belong to the species called Ustilago Sorghi. 
 
 This point in its identity having been settled, another diffi- 
 culty arose when a study was made of the spore formation of the 
 fungus. This showed that it agreed in this respect with the genus 
 Cintractia rather than with Ustilago, and if we are to regard these 
 as distinct genera, our fungus must be considered as belonging to 
 the former. Endothlaspis Sorghi of Sorokine, as has been stated, 
 is now referred by De-Toni questioningly to Cintractia, and what 
 was described originally as a quite distinct smut is really rather 
 closely related to our form. It is not unlikely that an examina- 
 tion of the spore formation of Ustilago cruenta would also show 
 something of this character. A careful examination of the type 
 specimens and of collections obtained from the different countries 
 where these smuts have been reported, together with a study of 
 their spore formation and germination, is needed to bring out their 
 true systematic relationships. However, having settled upon the 
 identity of our form as a Cintractia and as the species commonly 
 called Ustilago Sorghi, let us next consider its hosts and distribu- 
 tion. 
 
 HOSTS AND DISTRIBUTION. 
 
 /;/ general. This smut has been reported from a number of 
 the countries of southern Europe, also from Africa, Asia, and the 
 United States; and has for its host several of the different varieties 
 of Andropogon Sorghum. It was brought to the United States 
 through imported seed of these plants. Just when and where it 
 first made its appearance it is impossible to state ; but from the 
 ease with which it attacks broom-corn it was probably at the place 
 where that plant was first largely grown. The first printed refer- 
 ence that has been found is that made by Trelease, in his " Pre- 
 liminary List of Parasitic Fungi of Wisconsin," printed in 1884. 
 
 1 Untersuchungen aus dem Gesammtgebiete der Mykologie u: 43-51. 9 Ibid 
 5: 91-93. 8 Ibid 12: 120 
 
376 BULLETIN NO. 47. [March, 
 
 In this he mentions the finding of the fungus at Madison, and also 
 states that Sturtevant reports it from New York and Farlow from 
 the District of Columbia, in all three cases on plants raised from 
 imported Chinese seed. Professor Farlow in answer to inquiries 
 concerning the Columbia specimen writes that it was sent to him 
 from the Department of Agriculture at Washington and was 
 taken from sorghum grown in New Jersey in 1882. In 1889 
 Webber reported the finding of the smut on Millo maize in 
 Nebraska, and in 1890 Failyer and Willard found the same on 
 several imported varieties grown for the first time at the Kansas 
 Experiment Station. Professor Hitchcock in answer to a letter 
 gives the following plants upon which it has been collected in 
 Kansas: sorghum (Early .Amber, Rangoon, Red Liberian, and 
 many unknown varieties), broom-corn, Kafir corn. Though not 
 reported from Ohio so far as can be learned, it probably has 
 occurred there, as considerable broom-corn has been raised in 
 that state. 
 
 In Illinois. The first collections made in Illinois that are 
 represented in the herbarium at the University of Illinois were 
 those made by M. B. Waite in August, 1887, at Urbana. In 1888 
 in the Proceedings of the American Society of Microscopists, 
 Burrill notes the smut as occurring in this state on both broom- 
 corn and sorghum, and this is the first printed reference to the 
 smut here that has been found. No further collections or study 
 was made until the spring of 1894, when John Marten, assistant to 
 the State Entomologist, in studying the insect pests of broom- 
 corn at Arcola, brought specimens to the botanical department 
 with the report that this was considered one of the worst pests of 
 the plant in that vicinity. The study of the fungus in its relation 
 to broom-corn was then undertaken by the botanical department 
 of the Experiment Station, the results of which are given in this 
 bulletin. 
 
 INJURY AND LOSS. 
 
 Effect of attack. The importance of a fungous disease depends 
 in great part on the place and character of its attack. What is 
 the effect of this fungus upon its host? As with the smuts of 
 wheat and oats, one cannot tell the infected plant from the free 
 until the floral parts are protruded through the upper leaves. 
 Examination then shows that the infected plants have the place 
 of the seed occupied by a usually enlarged body, having on the 
 outside a reddish covering and within a dusty mass of spores. 
 All the seeds of an infected panicle are usually destroyed. The 
 first noticeable injury, then, is the prevention of seed formation. 
 
BROOM-CORN SMUT. 377 
 
 In the case of broom-cornr this loss is not nearly so serious as in 
 the case of those cereals that are raised especially for the seed. 
 
 An examination of the brush of an infected plant, unfortu- 
 nately, shows that it is of a very inferior grade, usually almost 
 worthless. Here, then, is a much more important loss, for the 
 brush is the part for which broom-corn is raised. Good broom- 
 corn has the rays of about uniform thickness and length and all 
 springing from a series of very contracted nodes so as to give 
 them about the same point of origin. In the case of infected 
 plants these internodes are usually elongated, and the rays are of 
 unequal lengths, so that there are a series of irregular rays arranged 
 on an elongated and thickened central axis qualities very unde- 
 sirable. Among growers of broom-corn this elongated and 
 thickened axis is not always recognized as the work of the fungus. 
 This is probably due to the fact that occasionally plants apparently 
 free from the fungus show brush of this character. Such are but 
 tendencies to a reversion toward the original type of the plant; 
 and, possibly, even in such cases an imprisoned vegetative state 
 of the fungus cut off from spore formation may at times be the 
 inciting cause. It is a fact, however, that in the many hundreds 
 of smutty panicles examined this tendency to spread out the con- 
 tracted axis was always more or less manifested. The number of 
 large normal sized rays is also less on such a plant. For instance, 
 in each of two different varieties the principal rays were counted 
 on ten free and ten affected plants selected at random. In every 
 case the number in the free plants exceeded those in the infected, 
 while the average for one was fifty-five on free plants and thirty- 
 three on infected, and for the other was forty-eight on free and 
 thirty-seven on infected plants. The energy in such plants has 
 gone into the elongated axis and not in enlarging all the rays. 
 
 Smut may also produce some damage by the spores settling 
 on the brush when this is gathered with moisture on it. These 
 stick to the plant when the moisture evaporates, and although 
 they may in part be shaken off the appearance of the brush is 
 still \ ery apt to be affected. This, however, must not be con- 
 fused, as it is by some, with the trouble that arises when broom- 
 corn is stored wet or in a damp place. Under such a condition a 
 saprophytic fungus of an entirely different nature is very apt to 
 appear on the plants, causing them to have a deadened color and 
 to become blackish where the fungous threads show. This trouble 
 affects very decidedly the color and strength and consequently 
 the value of the brush. Smut is, finally, a bad thing because of 
 the disagreeable dust that is produced when plants so affected are 
 thrashed. 
 
378 BULLETIN NO. 47. {March, 
 
 Abundance. A second factor that determines the importance of 
 a fungous disease is its abundance or distribution. What per cent, 
 of broom-corn plants are infected by smut, and how does this per 
 cent, vary from year to year? In 1895 Mr. Duncan, of the firm 
 of Duncan & Tarbox, broom-corn dealers at Arcola, said in re- 
 sponse to inquiries that broom-corn had been raised in that region 
 for thirty-five years, and while at first smut was not noticed it had 
 gradually increased in amount. Mr. B. F. Cox, a dealer at the 
 same place, also expressed a belief that smut was more abundant 
 than formerly, and gave as a rough estimate that -an average of 
 one per cent, of the plants were smutty. An examina- 
 tion of a few fields in the vicinity that year showed them usually 
 with less than one per cent, smutted. One very smutty field, 
 however, gave in parts of it twenty per cent. The few growers 
 seen seemed to think that smut was less than usual, though a year 
 or two previous it had been unusually abundant. In 1896 letters of 
 inquiry to various buyers and raisers in the vicinity of Arcola and 
 Tuscola brought the uniform reply that it had been a year in 
 which broom-corn was quite free from smut. 
 
 In our experiments here broom-corn, raised from seed such 
 as is ordinarily planted, gave in different plats during the two 
 years yields varying from one to twenty per cent, smutty; while 
 that raised from very smutty seed gave from ten to fifty per cent. 
 In 1896 the plants here, unlike those in the broom-corn district, 
 were unusually smutty. It is generally true that the seed that is 
 ordinarily planted produces plants in which the amount of smut 
 varies from practically nothing up to three to five per cent., or, 
 under exceptionally favorable conditions for the fungus, a still 
 higher per cent, may be expected; while seed that is very smutty 
 is always likely to give a crop with considerable smut, the per 
 cent, of which under conditions favorable to it becomes very large. 
 
 Value of crop. The importance of a fungous disease depends 
 lastly upon the value of the host as a commercial plant. In the 
 United States broom-corn is largely raised in parts of Kansas, 
 Illinois, and possibly in a few other states. The area devoted to 
 its culture in 1895 was estimated at over two hundred thousand 
 acres. 1 Of this area Kansas 2 claimed about one hundred thirty- 
 five thousand acres, producing a crop valued at over one million 
 two hundred twenty thousand dollars. The next year, however, 
 the acreage dropped to less than forty thousand. The secre- 
 tary 3 of the State Board of Agriculture for Illinois gave the area in 
 this state for 1895 as over twenty-five thousand acres, a slight 
 
 'Irrig. Age 9: Ja. 1896. 2 Rep. St. Bd. Agr. Kans. 16:794. 1896. 3 Statist. 
 Rep. 111. St. Bd. Agr. Dec. 1895 : 5. 1895. 
 
BROOM-CORN SMUT. 379 
 
 decrease from the preceding year. This Illinois acreage gave a 
 yield of over eighty-five hundred tons, the value of which, esti- 
 mated at the average price of the time, was over three hundred 
 thirty thousand dollars. Broom-corn, while raised in a small way 
 in a number of different counties, is extensively grown in Coles 
 and Douglas only, situated in central eastern Illinois. Here it is 
 one of the principal crops, amounting to three-fourths of all that 
 is raised in the state. 
 
 Financial loss. Judging from the above facts can this smut 
 be counted as an important pest? In other words, is it injurious 
 enough to merit attempts at prevention? If the seed of broom- 
 corn was the part for which the plant is raised (its loss when at- 
 tacked by the smut usually being total and the per cent, of in- 
 fested plants being easily estimated) the loss in dollars in partic- 
 ular cases or even in general for a district could be fairly esti- 
 mated, as is done in the case of smutted oats and wheat ; but as 
 the case is an estimate of loss would be largely guess work. No 
 aim, therefore, is made here to estimate the loss other than to 
 state that it is often great enough to make preventive measures 
 desirable. That it is at least serious enough for this seems to be 
 the uniform opinion of those interested in the culture of the 
 plant. In order to determine the estimate placed upon the fun- 
 gus a number of letters were sent to prominent growers of broom- 
 corn at Arcola and Tuscola, and several of the answers to three 
 of the questions asked are given here : 
 
 1. Is smut one of the prominent enemies of broom-corn, and would it be 
 of much benefit if it could be prevented? 
 
 2. Do you use means to keep broom-corn free from it? What? 
 
 3. How does it injure broom-corn? 
 
 i. Yes. 2. Plant seed that is not affected with it. 3. By blackening 
 it after it gets wet before it is thrashed. Most of the heads that have smut on 
 them are of no account. 
 
 Arcola, 111. W. C. CUPPY. 
 
 i. Smut is an enemy of broom-corn, and it would be a decided benefit to 
 prevent it. 2. The means we use is to select seed that has no smut on it. 3. 
 You lose the head that has smut on it, and if the cane is damp when you seed 
 it, it colors the rest and injures the sale. 
 
 Tuscola, 111. A. B. SAWYER. 
 
 i. Smut is one of the enemies, and it would be an advantage if prevented. 
 2. I am careful to use seed that has not been infected with it. 3. If cleaned 
 when damp or with dew on it darkens the brush. 
 
 Arcola, 111. D. S. HARRIS. 
 
 i. Yes. 2. No. 3. It makes it a light or white color and the brush 
 is brittle and of light weight. I think the time it is planted and the season 
 has a good deal to do with it, as some years it is worse than others. It was 
 the worst in 1893, a very dry season after the tenth of June. 
 
 Tuscola, 111. NATHANIEL MOORE. 
 
380 BULLETIN NO. 47. r _March, 
 
 I. Yes. 2. Yes, by washing in copperas. 3. It makes it bad to 
 handle all the way through, and if it rains while it is on the table in the field it 
 causes it to turn black. I think that it is in the seed that is planted, and the 
 longer seed is planted (that is seed that has smut in it or in the field from 
 which it came) the more smut there will be. 
 
 Arcola, 111. CHARLES WESCH. 
 
 I. Yes. In my opinion it would. 2. Only by trying to secure seed 
 free from smut. 3. By blasting, causing large fiber of a coarse, worthless 
 quality. Also when cleaned when damp it adheres to the other heads, turning 
 them black. 
 
 Arcola, 111. F. G. HASTEN. 
 
 Let us now turn from the economical consideration of smut 
 and study it in detail as a plant in its various phases of develop- 
 ment. 
 
 LIFE HISTORY. 
 
 Nature of smut. We have been proceeding so far on the 
 assumption that the nature of smut is understood by the reader. 
 It is a fact, however, that all growers of broom-corn do not realize 
 that smut is a plant, though of low development, just as much as 
 'is broom-corn, which is one of high development. The vague ideas 
 held by some may be illustrated by the fact that such think smut 
 is the result of insect work, or that it is a " bastard growth due to 
 the effect of sorghum on broom-corn," etc. 
 
 Smut belongs to the very low group of plants called fungi 
 plants of very simple development, usually of very small size, 
 and destitute of the power of directly forming their food out of 
 mineral matter, moisture, and gases. This being the case, fungi 
 must get their food from either dead or living organic matter. 
 In the case of smut it gets its food from the living broom-corn 
 plant, and so it is called a parasitic fungus. Like broom-corn 
 it has a vegetative part concerned with obtaining the supply of 
 food and with growth, and a reproductive part concerned chiefly 
 with the production of future individuals like itself. The vegeta- 
 tive part is technically known as mycelium, and is composed of 
 thread-like cells concealed entirely within the tissues of the broom- 
 corn. The reproductive bodies are known as spores, and the 
 multitudes of these minute cells are what constitute the visible 
 portion of the fungus in the " smutted " parts of the host. 
 
 Spores. The character of the visible outbreaks seem to vary 
 somewhat in the different varieties. This is probably due to the 
 differences in the surrounding tissues or other peculiar character- 
 istics of each host. In general, however, a somewhat elongated 
 and thickened seed-like body is formed. In broom-corn this, 
 compared with the normal seed, is usually a slightly enlarged ovate 
 
BROOM-CORN SMUT. 381 
 
 or oblong formation. A careful examination of these while young 
 shows that they have taken the place of the young pistil and sta- 
 mens, rarely merely the former while the latter have come to a 
 somewhat normal development. Frequently these parts are infected 
 so early that they have become blended together and the identity 
 of the stamens entirely or nearly lost (pi. 3, fig. 6). In 1895 speci- 
 mens were found that varied considerably from this normal type. 
 Here the outbreaks were more elongated (half an inch) and with 
 somewhat closely appressed branches. Evidently these repre- 
 sented an infection of the whole flower, or possibly of more than 
 one flower. The specimens were thought at first to be a distinct 
 species, but the appearance and germination of the spores and all 
 gradations between this and the normal form showed the two to 
 be the same (pi. 3, fig. 7 and 8). The difference in appearance was 
 evidently only the result of an earlier and hence more widespread 
 spore formation. In all of these outbreaks there is on the outside 
 a somewhat reddish membrane, while the space within is taken up 
 with a dusty mass of spores, save in the center where there is a 
 distinct, slender and hard mass of tissue, referred to by Winter as 
 the "columella." 
 
 Examined under the microscope the individual spores have a 
 brownish color with a distinct olive tint, though in mass to the 
 naked eye they are of a very dark reddish brown color. They are 
 single celled bodies of a sub-spherical shape and from 5 to 8 
 thousandths of a millimeter in diameter, 1 though varying occasion- 
 ally from the above in both shape and size. The protoplasmic 
 contents fill the spore and are frequently somewhat granular so 
 as to give the spore wall the appearance of being minutely papillate. 
 
 Germination. When placed in water these spores germinate 
 readily. No other of the many smuts whose germination in water 
 we have tried has germinated so readily and vigorously as this. It 
 germinates equally well as soon as formed or when a year old. 
 Specimens kept in a dry room germinated whenever placed in 
 water at various intervals during more than three years, though 
 less abundantly and easily the last year. De Bary states that von 
 Liebenberg caused the spores to germinate after being in the 
 herbarium six and a half years. 
 
 The general character of the germination depends on the 
 fluid in which the spores are placed. In water, while there was a 
 difference in degree between different spores in the same culture, 
 and, while at different times perhaps all conditions were not ex- 
 actly the same and so varied the character somewhat, still the gen- 
 
 J This size may be better appreciated by the many readers when it is stated that 
 there are millions of these spores in each of the seed-like bodies. 
 
382 BULLETIN NO. 47. [March, 
 
 eral phenomena were as follows : Within six to ten hours after 
 being placed in the water many of the spores show the beginning 
 of germination by the appearance in each case of a minute 
 hyaline papilla, which gradually grows out into a thin -walled tube 
 having a rounded and slightly pointed apex, but showing no con- 
 striction where it emerges from the spore. Some spores have 
 shown this stage of germination within three hours after being 
 placed in the water. This germ-tube, or pro-mycelium, elongates 
 until it is three to five times as long as the diameter of the spore, 
 this being accomplished within less than twenty-four hours after 
 germination begins, frequently in about half that time. Two or 
 three cross-partitions are now formed at right-angles to the tube, 
 dividing it into three or four about equal cells. These septa are 
 rather faint at first, and while the tube is filled with protoplasmic 
 contents are not always clearly made out. A slight staining, how- 
 ever, serves to bring them out much clearer. At the end of one 
 or more of these cells a short and usually narrow outgrowth ap- 
 pears which bends over and fuses with the adjoining end of the 
 next cell. Usually this outgrowth is so closely appressed that it 
 appears as if the septum had not been formed clear across the 
 tube on that side (pi. 5, fig. 3). These form the so-called buckle or 
 knee joints, and the tube frequently has more or less of a bend 
 where they occur. In a number of cases these buckle joints were 
 seen to be formed by the union of protuberances extending from 
 each side of the septum. Not infrequently these slender out- 
 growths are less closely appressed to the tube and make quite a 
 growth before joining the pro-mycelium at some more remote 
 point (pi. 5, fig. 2). From these buckle joints, or the end of the 
 pro-mycelium, frequently a thread, usually much more slender 
 than the main tube, grows out to a varying length, forming what 
 I have called infection-threads, because of their similarity to those 
 produced by the sporidia. If these threads attain any consider- 
 able length, they show an irregular curving rather than a growth 
 in a straight line like the pro-mycelium. Sometimes the pro- 
 mycelium also gives rise to a lateral branch near the base of about 
 the same diameter as itself. Sporidia are generally produced, 
 though not always very abundantly. Occasionally one can be 
 seen forming either on the end of the pro-mycelium or at the 
 apex of one of the cells. It appears as a small outgrowth hav- 
 ing a very narrow connection with the tube, enlarges gradually 
 and is very easily broken from its connection, so that sporidia are 
 usually only seen free in the water. Usually they did not germ- 
 inate, neither did they seem to reproduce, yeast-like, after being 
 formed. Frequently a large part of the pro-mycelium is early cut 
 
BROOM-CORN SMUT. 383 
 
 off from the spore by an abstriction near the base. These free 
 bodies are somewhat like sporidia in appearance, but can be told 
 by their larger size and the presence of one or two septa. They 
 go through the same development as if remaining connected with 
 the spore. 
 
 The preceding germinations were produced chiefly in dis- 
 tilled water; but when large numbers of spores are placed in the 
 fluid, as was usually the case, possibly a little nutritive material is 
 also introduced. Whether the spores are immersed in an abund- 
 ance of water or are merely covered with a film so as to admit of 
 contact with the air has also something to do with determining the 
 character of germination. In the latter case the pro-mycelium is 
 more apt to run out into a slender thread which is many times the 
 length of the pro-mycelium and not so sharply marked off from it. 
 The protoplasm is confined to the distal end of this thread, the 
 empty part becoming regularly septate. In some few cases I found 
 that in time these threads even gave rise to sporidia and secondary 
 sporidia. The sporidia and secondary sporidia are also more apt 
 to be formed on and to adhere to the pro-mycelium. 
 
 In nutrient solutions the chief differences observed from the 
 preceding were the more luxuriant, though not necessarily more 
 abundant, germination, and the formation of more sporidia. In 
 the cases where a weak nutrient fluid of tomato-broth was used the 
 chief differences were the somewhat larger pro-mycelia, the pres- 
 ence in the fluid of more free sporidia, infection threads of greater 
 diameter and usually of greater length. In beef-broth this luxur- 
 iant growth of the pro-mycelium was still greater; the sporidia 
 were formed very abundantly and were not easily detached ; and, 
 while connected or when fallen off, formed secondary sporidia by 
 the yeast-like manner of sprouting; the sporidia were also larger, 
 especially in diameter, as were also the branches or infection- 
 threads that were formed. When the beef-broth became weakened 
 sufficiently, the sporidia ceased their sprouting and formed the 
 narrow infection-threads quite similar to those usually produced 
 in water from the pro-mycelium. 
 
 Infection of host. This apparently takes place through the 
 penetration of the epidermis by the infection-threads of the pro- 
 mycelium as well as by those of the sporidia. Entrance into the 
 plant can occur only when the cells are young, and successful 
 infection only through that part of the plant where the threads 
 can reach the growing tip of the plant before the tissues through 
 which it must pass are very old. Thus the germinating seed in its 
 early stages is the only place where broom-corn is liable to become 
 successfully infected. As a germinating plant becomes older and 
 
384 BULLETIN NO. 47. 
 
 its tissues harder of penetration by the threads, infection becomes 
 less possible until, at the time when the plant breaks through the 
 ground and its first leaves show, it is practically exempt from suc- 
 cessful infection. Brefeld has shown with Ustilago cruenta on a 
 similar host that the germs can enter the very young leaves of 
 even large plants, but can not form the mycelium fast enough to 
 reach the growing tip before it is cut off by the maturing of the 
 tissues. 
 
 In germination broom-corn .shows a common type among 
 grasses an epicotyl, or sort of an underground internode, is 
 formed connected at one end with the seed and at the other bear- 
 ing the leaf-sheath with the enclosed young leaves and growing 
 tips. The epicotyl usually lengthens enough to bring the leaf- 
 sheath above ground, and about this time the growth of the latter 
 is stopped so that it is soon pierced at its apex by the growing 
 leaves within. Young plants upon the seed of which spores were 
 placed before germination, after they had produced plants of 
 the above or a little later stage, were frequently examined for 
 mycelium ; when this was found it was most abundant at the junc- 
 ture of the epicotyl and leaf-sheath, and rarely extended very 
 far down into the epicotyl. Plants at. this age also became in- 
 fected when the leaf-sheath was removed and spores placed on 
 the young leaves at its base, but did not become infected when 
 the spores were merely placed on the outside of the base of the 
 leaf-sheath. The direction of the mycelium in all these cases 
 was chiefly toward the center of the plant and up. As this (region 
 near juncture of epicotyl and leaf-sheath) is the shortest path 
 through the plant tissues to the growing apex, it is the most cer- 
 tain and probably the most common place for successful infection, 
 and the earlier the threads enter the more certain they are to 
 reach the growing tip. After entering it is quite likely that the 
 threads spread in all directions, if there is no difference in resist- 
 ance ; but the maturing cells gradually limit this until finally 
 only the mycelium that has reached the young growing parts 
 keeps up a vigorous growth. 
 
 Mycelium. When once the infection-threads succeed in enter- 
 ing the plant at the proper place and time, their further growth is 
 assured by the nourishment that is taken from the plant, and so 
 they soon become independent of the sporidia or spores to which 
 they are attached on the outside. They rapidly grow into long, 
 irregularly branched, colorless and thin walled threads that ramify 
 through the tissue of the plant. The diameter of these threads 
 (2-4 microns) is considerably enlarged from that of the infection- 
 thread, whose very small diameter is more favorable for penetration 
 
f$9?.] BROOM-CORN SMUT. 385 
 
 of the epidermal cells. These threads now constitute the mycelium 
 of the fungus. This is not confined to the intercellular spaces but 
 runs as readily through the cells. It is found most abundantly in 
 patches in the parenchyma cells which in the epicotyl form a band 
 several cells deep surrounding a central cylinder of the wood cells. 
 At the juncture of the leaf-sheath where the central cylinder 
 begins to separate into the distinct bundles, the mycelial threads 
 run into the parenchyma cells surrounding the bundles. They 
 were also found in the base of the leaf-sheath and in the lower 
 parts of the first leaves. 
 
 At first the threads are filled with protoplasm, but as they 
 become older this is more or less lost, and septa are found at 
 irregular intervals; frequently the cell walls are swollen or the 
 contents so changed that the lumen of the thread is not distinctly 
 made out. In the older infected parts there is frequently some 
 discoloration of the threads and of the surrounding plant cells, but 
 in parts but newly infested there is no disturbing condition shown. 
 As these threads penetrate further in the plant they become more 
 limited to the intercellular spaces, and the branches that penetrate 
 into the cells for nourishment assume more of a special appear- 
 ance (pi. 4, fig. 5). Reaching the young pith cells a short distance 
 below the growing point as new cells are formed they gradually 
 become infested and thus the fungus follows the upward growth 
 of the plant during the entire season. After an infected plant has 
 made its full growth, the mycelium can often be found scattered 
 through the pith in the various internodes generally most abundant 
 in the region of the nodes. Thus mycelium has been found in the 
 very base and in the very apex of plants, a distance of eight or 
 ten feet apart. It is very improbable, however, that there is a 
 continuous connection of the mycelium for even any great part of 
 this distance, for according to Brefeld, the lengthening of the 
 internodes tends to destroy the continuity of the threads. It is 
 always only the mycelium in the vicinity of the tip of the plant 
 that is the active growing part of the fungus. 
 
 Spore formation. Such is the history of the fungus until the 
 time the broom-corn begins to form its flower parts, and all this 
 time the infected plant, so far as appearance goes, is similar to 
 the one that is not infected. The mycelium penetrates the young 
 ovaries and stamens usually before they are very much differen- 
 tiated. If this penetration is very early, then the stamens and 
 ovary are not differentiated from each other in the smutted body ; 
 but if the fungus has been backward in its penetration, then the 
 smutted part shows ovary and stamens more or less grown together 
 but still so that they can easily be made out as these organs; 
 
386 BULLETIN NO. 47. [March, 
 
 occasionally the penetration is even so late that the stamens are 
 free from the spores, only the ovary containing them. Flowers 
 of an infected plant were examined that were so young that the 
 stamens and ovary showed only as small undifferentiated out- 
 growths of cells from the growing point, and while no mycelium 
 was definitely made out in these, still it was found among the 
 young cells in their vicinity, thus indicating that entrance of the 
 threads may take place very early in the formation of the essential 
 organs of the flower. It is also a fact that by the time the flower 
 parts are thrust into sight from the enfolding bases of the leaves 
 the smut spores are in part fully developed and apparently ready 
 for germination. 
 
 Unfortunately specimens showing the condition of the fungus 
 after penetration of the essential organs but before spore forma- 
 tion were not preserved for examination, and so peculiarities of 
 the mycelium, if such exist, immediately preceding spore forma- 
 tion can not be given here. However, examination of the very 
 young spore bearing bodies, before all the mycelium has been 
 changed into spores, has given information concerning some very 
 interesting changes that take place in spore formation, and shows 
 that in this species it is quite different from that attributed to 
 Ustilago as a genus. 
 
 Evidently, after entrance into the essential organs, the forma- 
 tion of mycelium soon takes place most abundantly in the cells 
 immediately beneath the epidermis, so that in time this becomes 
 separated from the rest of the plant cells by a dense mass of fun- 
 gous threads, which, as they multiply and change into spores, 
 crowd inward the inclosed cells and stretch outward the layer of 
 epidermal cells, the final result being the seed-like smutted part 
 with its membrane on the outside, mass of spores within, and the 
 columella in the center. 
 
 Sections through these infected bodies while quite young 
 show the origin and character of these parts. Taking first the 
 columella we find that it narrows somewhat irregularly from the 
 base toward the apex and terminates before reaching the end of 
 the spore bearing body. It forms a stiff, slender column that 
 remains after the rest of the body has crumbled to pieces. If 
 stamens go to make up part of the infected body but are made 
 out as free bodies at the apex, the columella will send out a little 
 branch into each of these originating from below where the stamen 
 loses its identity with the main body ; or if the stamens are 
 entirely free from the ovary but still infected each will have its 
 own columella. These columellas evidently are thus the fibro- 
 vascular parts and the undestroyed parenchyma cells that were 
 
1897.} BROOM-CORN SMUT. 387 
 
 intended for the formation of the essential organs of the flower. 
 In stained sections they plainly show considerable of the sterile 
 fungous threads ramifying through them. 
 
 Proceeding now to the membrane on the outside, the micro- 
 scope shows that it is not entirely made up of the epidermal cells, 
 but is rather a false membrane having on the outside the still more 
 or less distinct epidermis, but beneath this a tissue of sterile fun- 
 gous threads which forms its greater thickness. These sterile 
 threads are quite different from the usual threads of the mycelium, 
 especially when fully matured, and exhibit some variations in 
 the hosts that belong to varieties other than- broom-corn. The 
 threads tend to break up into their component cells or short rows 
 of these. The cells become rounded at their ends and assume a 
 sub-spherical to irregular oblong shape. The walls are more or 
 less thickened. Though usually empty they may contain some 
 contents. The cell walls always retain their hyaline appearance 
 and because of this and their large size and grouping together are 
 in no way likely to be confused with the fertile spores that occur 
 just beneath this membrane. 
 
 The sections also show that the spores are not formed simul- 
 taneously from the fertile threads that exist between the envelop- 
 ing sterile cells of the membrane and the central plant cells of the 
 columella, but that there is a progressive formation from without 
 toward the columella or centripetally. It is quite probable, too, 
 that this formation begins first at the free end, so that the oldest 
 spores would be those near the top of the infected body. The 
 formation of the spores so far as could be gathered from the 
 youngest specimens at hand was as follows. Beginning next the 
 columella the section presents an appearance as if the fungous 
 threads had entirely gelatinized their walls, which, with the dis- 
 solved cell contents, formed a colorless amorphous stratum in 
 which were imbedded the protoplasmic contents as very distinct, 
 narrow and usually short and simple strands, almost bacteria-like 
 in appearance. In these fine strands, less than a micron in diam- 
 eter, are to be made out more highly refractive granules, possibly 
 nuclear functioning bodies. As we proceed outward in the section 
 the strands become irregularly contracted and apparently larger 
 until we meet with those that are roundish and reforming a visible 
 cell wall. Further out in the section the cell wall is more dis- 
 tinctly made out and becomes tinted. From here they grade into 
 spores that are fully developed as to size, shape and color but are 
 bound very closely together, while the outermost spores do not 
 so firmly adhere to one another. The transformation is generally 
 gradual, there being no sharp line of separation, that of color 
 being most marked. There is more or less of a radial effect in 
 
388 BULLETIN NO. 47. [Marc /t, 
 
 the undeveloped parts, as if the formation was not entirely annu- 
 lar but as if various radial units had given origin to the formation 
 but had more or less lost their individuality by lateral fusion. 
 Perhaps projecting wedges of plant tissue give rise to this 
 effect in part, but where these are apparently absent there are seen 
 radial strands where the gelatinization of walls, etc., are not so 
 marked. In the above manner gradually all of the spores are 
 matured. When this has occurred, the spore mass dries out and 
 becomes dusty, and the enveloping membrane sooner or later 
 becomes ruptured and the spores are easily scattered by the wind. 
 From the abov^description it is seen that the spore formation 
 is quite different from that usually described for Ustilago. How- 
 ever, an examination of very young outbreaks of Ustilago Zeae 
 (Beckm.) Unger in the leaves of corn showed that there is con- 
 siderable resemblance. Here I found that frequently small groups 
 of spores were formed from a mass of mycelium encircled on all 
 sides by plant cells ; and, while there was a less decided geletiniza- 
 tion of walls and re-arrangement of protoplasmic strands, there 
 was still a progression of spore development, though it was not 
 nearly so marked as in broom-corn smut, and the central spores 
 seemed to be the ones first formed. There were also threads more 
 isolated in the plant tissue that were forming spores after the 
 manner usually described for this genus. On the other hand an 
 examination of Cintractia as described by Cornu 1 and Trelease, 2 and 
 as exhibited by sections through rather mature specimens of 
 Cintractia axicola and Cintractia Junci (species with which the 
 above authors worked) shows that the fungus on broom-corn is a 
 Cintractia, if that is entitled to generic distinction from Ustilago. 
 In both of these species, as we found with broom-corn, there is a 
 membrane composed of sterile cells and epidermis, but with them, 
 unlike in broom-corn, the outbreak occurs just beneath the epi- 
 dermis at the base of the flower peduncles; and, as the enclosed 
 woody portion is normally developed, the strain of the spore 
 formation of necessity ruptures the surrounding membrane and it 
 soon falls off, leaving the spores naked but more or less agglu- 
 tinated. These have been developed centripetally around the 
 central cylinder of plant tissue, similarly to those of broom-corn 
 smut around the columella. In Cintractia axicola there is also 
 the radial effect but shown much more prominently. The germi- 
 nation of Cintractia Junci is somewhat similar, at least in water, 
 to that of broom-corn smut. The place of outbreak and the 
 appearance of the spores, however, in both these species is dif- 
 ferent from those of broom-corn. 
 
 'Ann. Sci. Nat. Bot VI. 15: 277-279. 1883. 
 "Bull. Torr. Bot. Club 12. 69-70. Jl. 1885. 
 
1897.] BROOM-CORN SMUT. 389 
 
 EXPERIMENTS. 
 
 Object. To determine some of the preceding facts concern- 
 ing the life history of the fungus and also to find out whether it 
 was a trouble that could be prevented, it was necessary to carry 
 on a number of experiments with plants both in the laboratory and 
 in the field. The indoor experiments were along two lines. First, 
 to determine by infection the place or places on the broom-corn 
 through which the smut gains entrance. Second, to determine 
 the effect of hot water on the germination of the seeds of broom- 
 corn and of the spores of the fungus. The field experiments 
 were chiefly to compare the amount of smut produced in plants 
 whose seed was treated with hot water with that produced in 
 those whose seed was not treated. 
 
 Infection experiments. While many attempts were made to 
 infect plants by placing spores on the seed or on very young 
 parts of the germinating plants, the success of which was deter- 
 mined later by the presence of mycelium in the tissues, the per 
 cent, of plants that became infected was not very large. This was 
 doubtless due in part to the use of spores, instead of pure cultures 
 of sporidia of the right age for infection the method used by 
 Brefeld. The spores, however, always germinated very easily and 
 abundantly, and it was thought they would furnish a source for 
 infection equal to that which exists in nature. The spores were 
 used also to determine, if possible, whether the fine threads of 
 the spores that we have called infection-threads were really of 
 that nature. The experiments were mostly made with seed treated 
 with hot water, and germinated in soil or sand free from spores. 
 The germinating seeds were then moistened at certain places, or 
 at certain ages, with water containing spores. After growth vary- 
 ing from a day or so to two or three weeks either the epidermis 
 was examined for evidences of penetration or sections were cut 
 and examined for mycelium. 
 
 It seems to be a fact that there is a close relationship between 
 the stage of germination of the spores and the place or age of the 
 parts through which infection takes place. These conditions 
 seemed to be best adjusted by placing the spores on the seed and 
 allowing both to germinate together in earth, at least most of the 
 plants that became infested were those so treated. Although many 
 trials were made by placing germinated or ungerminated spores 
 on the germs at various places and ages, we were not successful in 
 our examination of the epidermis afterward in finding spores or 
 sporidia on the outside that were connected with mycelium 
 within. It was a common thing, however, to find vigorously ger- 
 minating spores in which there were no signs of the threads pene- 
 
390 BULLETIN NO. 47. \March, 
 
 trating the epidermis. A few spores were found in one case 
 where there seemed to be some attempt on the part of the infec- 
 tion-threads to push down between the cell walls of the epidermis. 
 Mycelium, in the sections, was frequently found in the epidermal 
 cells, in a few cases showing a narrowed part at the end of a 
 thread as if entrance had been gained near that point (pi. 4, fig. 3). 
 The mycelium was always most abundant in the region where 
 epicotyl and leaf-sheath joined, and very little, if any, toward the 
 seed end of the epicotyl. This would seem to indicate, at least in 
 these cases, that if penetration took place through the epicotyl it 
 did so very early, or only at the upper end if later. That it is 
 largely a question of young tissue that can be penetrated easily is 
 shown by the fact that plants that had one or two leaves through 
 the sheath, but with this still fresh, became infected when this was 
 removed and spores placed on the base of the exposed leaves 
 where the cells were quite young; while plants not nearly so old 
 did not become infected when spores were merely placed at a 
 corresponding position but on the outside of the normally exposed 
 parts of the sheath, the cells there being more mature. In the 
 field experiments where spores were placed on young leaves at 
 different ages of the plants, it was shown that successful infection 
 did not take place in these cases, probably, because even if pene- 
 tration was successful, the threads were not able to reach the 
 growing tip. 
 
 Effect of treatment on seed. In the treatment with hot water it 
 was desired to find out at what temperature the treatment began 
 to injure the germinative power of the seeds, how much higher 
 this temperature is than that at which the spores are killed, and 
 whether this difference, if any, was great enough to permit of the 
 .treatment as a practical operation. Two vessels of water were 
 used one at about the required temperature in which the seeds 
 in a small bag were placed to take off the chill, and the other at 
 the desired constant temperature, in which the seeds were im- 
 mersed for the required time. The thermometer was placed in- 
 side the bag so that it would register the temperature of the 
 water immediately surrounding the seeds. After treatment one 
 hundred seeds were selected and, with a similar number of un- 
 treated as a check, were placed in a Geneva germinator. Every 
 twenty-four hours all seeds that had germinated were removed 
 and the number noted. 
 
 In the following table the results of the treatments are given. 
 In some cases the same treatment was tried twice but at different 
 times of the year. The different lots were treated at various 
 times during the fall and winter and germinated in a room where 
 
BROOM-CORN SMUT. 
 
 391 
 
 there was some variation of temperature. The conditions for 
 each treated lot and its check were, however, exactly the same. 
 From the table it will be seen that there was practically no differ- 
 ence between the treated and untreated lots up to the tempera- 
 ture of 132 F., and 135 F. for ten minutes. From here on there 
 was somewhat of a retardation of germination. The treatment 
 at 140 F. and higher seems on some occasions also to have killed 
 some few seeds. These results, of course, might vary with the 
 seed used the older the seed the less likely it would be to stand 
 the higher temperatures; different varieties might vary slightly 
 in resistance power; seeds freed from their glumes would be in- 
 jured more easily than seed tightly invested by the glumes. The 
 results, however, show that broom-corn seed has a resistance 
 power against hot water higher than that of our other common 
 agricultural grasses, and consequently there would be less chance 
 of injury to the seed in the treatment, other conditions being the 
 same 
 
 GERMINATION OF BROOM-CORN SEED TREATED WITH HOT WATER. 
 
 Treatment of seeds. 
 
 Hours after placing in germinator. 
 
 O 
 n 
 
 3 
 
 % failed. 
 
 24 
 
 48 
 
 72 
 
 96 
 
 1 20 
 
 144 
 
 1 68 
 
 192 
 
 216 
 
 240 
 
 264 
 
 Seeds in hot water, 120 
 F for 15 min 
 
 Treated 
 Check 
 
 o 
 
 o 
 
 13 
 
 II 
 
 47 
 61 
 
 21 
 19 
 
 5 
 
 i 
 
 6 
 o 
 
 5 
 4 
 
 
 
 
 
 97 
 96 
 
 3 
 4 
 
 
 Seeds in hot water, 130 
 F. for 5 min 
 
 Treated 
 Check 
 
 2 
 
 4 
 
 8 
 
 IO 
 
 
 63 
 6 4 
 
 14 
 
 12 
 
 2 
 2 
 
 2 
 2 
 
 4 
 
 2 
 
 
 
 
 95 
 96 
 
 5 
 4 
 
 
 Seeds in hot water, 130 
 F. for 10 min 
 
 Treated 
 Check 
 
 i 
 
 
 
 5 
 6 
 
 
 7 6 
 
 82 
 
 
 8 
 
 5 
 
 3 
 O 
 
 I 
 
 3 
 
 2 
 2 
 
 
 
 96 
 98 
 
 4 
 
 2 
 
 
 Seeds in hot water, 130 
 F for 1 5 min 
 
 Treated 
 Check 
 
 3 
 
 I 
 
 7 
 
 2 
 
 60 
 
 55 
 
 18 
 37 
 
 9 
 i 
 
 5 
 
 
 
 
 
 
 96 
 96 
 
 4 
 4 
 
 
 Seeds in hot water, 130 
 F. for 1 5 min 
 
 Treated 
 Check 
 
 o 
 o 
 
 8 
 8 
 
 30 
 36 
 
 28 
 30 
 
 13 
 13 
 
 2 
 2 
 
 
 2 
 
 2 
 
 I 
 
 2 
 
 3 
 
 2 
 
 95 
 
 IOO 
 
 5 
 o 
 
 
 Seeds in hot water, 132 
 F for 5 min . . . 
 
 Treated 
 Check 
 
 I 
 o 
 
 18 
 23 
 
 50 
 
 
 23 
 
 18 
 
 3 
 
 2 
 
 
 
 
 
 
 95 
 94 
 
 5 
 6 
 
 
 Seeds in hot water, 132 
 F for lo min .... 
 
 Treated 
 Check 
 
 
 
 
 8 
 29 
 
 44 
 34 
 
 24 
 
 22 
 
 14 
 
 5 
 
 7 
 7 
 
 O 
 
 I 
 
 i 
 
 i 
 
 
 
 
 98 
 99 
 
 2 
 I 
 
 
 Seeds in hot water, 135 
 F. for 5 min 
 
 Treated 
 Check 
 
 o 
 I 
 
 12 
 
 16 
 
 33 
 34 
 
 24 
 19 
 
 19 
 14 
 
 6 
 
 5 
 
 3 
 i 
 
 i 
 o 
 
 2 
 3 
 
 2 
 
 
 IOO 
 
 95 
 
 
 
 5 
 
 
 Seeds in hot water, 135 
 F. for 10 min 
 
 Treated 
 Check 
 
 o 
 o 
 
 2 
 17 
 
 33 
 
 37 
 
 27 
 
 25 
 
 18 
 6 
 
 3 
 6 
 
 5 
 o 
 
 3 
 o 
 
 2 
 I 
 
 
 
 93 
 92 
 
 7 
 
 8 
 
 
 Seeds in hot water, 135 
 F. for 1 5 min 
 
 Treated 
 Check 
 
 3 
 3 
 
 50 
 67 
 
 25 
 
 12 
 
 
 1 
 
 5 
 
 5 
 
 5 
 i 
 
 i 
 i 
 
 
 
 
 99 
 96 
 
 i 
 
 4 
 
 
 Seeds in hot water, 135 
 F. for 1 5 min 
 
 Treated 
 Check 
 
 i 
 o 
 
 5 
 8 
 
 34 
 51 
 
 26 
 24 
 
 13 
 
 12 
 
 8 
 5 
 
 5 
 o 
 
 I 
 O 
 
 2 
 
 O 
 
 I 
 
 96 
 
 IOO 
 
 4 
 
 
 
 
 Seeds in hot water, 140 
 F. for 1 5 min 
 
 Treated 
 Check 
 
 2 
 
 3 
 
 12 
 6 7 
 
 2 3 
 
 12 
 
 
 17 
 
 7 
 
 IO 
 
 5 
 
 9 
 i 
 
 4 
 i 
 
 
 
 
 77 
 96 
 
 23 
 4 
 
 
 Seeds in hot water, 150 
 F. for 15 min. ... 
 
 Treated 
 Check 
 
 I 
 II 
 
 o 
 o 
 
 28 
 60 
 
 2 
 
 6 
 
 22 
 
 43 
 
 4 1 
 17 
 
 23 
 
 ii 
 
 7 
 
 5 
 
 2 
 
 25 
 17 
 
 2 
 I 
 
 5 
 
 
 3 
 o 
 
 O 
 2 
 
 2 
 
 
 88 
 
 95 
 97 
 
 12 
 2 
 
 5 
 
 
 Seeds in hot water, 150 
 F. for 15 min 
 
 Treated 
 Check 
 
 2 
 I 
 
392 BULLETIN NO. 47. {March, 
 
 Effect of treatment on spores. The effect of hot water on the 
 germination of the spores was studied at the same time. Smutted 
 seed-like bodies (broken and entire) were placed with the seed to 
 be treated, also spores placed on the inner surface of a small piece 
 of paper that was folded once. In the last case the spores were 
 placed on the paper in order that they could be found after treat- 
 ment, and were supposed to be subjected to the same temperature 
 as spores that might occur on the surface of seeds. Possibly the 
 paper furnished some little protection against the heat, but cer- 
 tainly not so much as would be furnished those spores that had 
 slipped down between the glumes of the seeds. After treatment 
 some of the spores from the interior of unbroken smutted bodies, 
 from the broken ones and from the paper, together with untreated 
 spore as a check, were placed in water in culture cells and exam- 
 ined with the microscope from time to time to determine the 
 amount and time of their germination. The results, abbreviated 
 from the notes taken at the time, are as follows : 
 
 No. 1028. In hot water 130 F. for 5 min.; spores taken from inside of unbroken 
 body. Examined 17 hours after placing in culture cells, and found spores germinating 
 very actively, probably from 50 to 75 per cent.; stage of germination possibly not quite 
 so far advanced as in the check. 
 
 No. 1029. Treatment same ; spores from surface of paper. Examined same time as 
 above, and found not over one or two per cent, germinating and these much behind 
 stage of development of those in the check. 
 
 No. 1030. Check, or spores not treated. When examined with above found nearly 
 every spore germinating and most of them quite far advanced. 
 
 Later examination showed little change in the relative amounts of germination of the 
 above. 
 
 No. 1035. In hot water 130 F. for 10 min.; spores from inside of unbroken body. 
 Examined 24 hours after placing in culture cells, and found about 5 per cent, had germ- 
 inated and these in about the same stage as check spores. . - 
 
 No. 1034. Treatment same; spores from surface of paper. At end of 24 hours 
 about 3 per cent, had germinated and these were not so far advanced as in check. 
 
 No. 1036. Check. About 50 per cent, had germinated and these well advanced. 
 
 Have no data as to later examinations and conditions. 
 
 No. 1045. In hot water 132 F. for 10 min.; spores from inside of body. Exam- 
 ined 24 hours after placing in culture cells and found less than a dozen germinating 
 spores. At end of 48 hours, however, the spores had germinated abundantly, though not 
 so abundantly as in check. A second culture made 24 hours after treatment and taken 
 from a different infected body that had quite a tough and unbroken membrane showed 
 no retardation in germination at the end of 24 hours, and also had about as many spores 
 germinating as in the check lot. 
 
 No. 1044. Treatment same ; spores from surface of paper. Results the same as in 
 first example of 1045. 
 
 No. 1046. Check. At end of 24 hours germinated spores were very abundant and 
 very well advanced. 
 
 No. 1049. In hot water I34-5 F. for 5 min.; spores from inside of an unbroken and 
 firmly covered body. Examined at end of 24 hours and found germination well ad- 
 vanced, and even more abundant than in check slide. 
 
BROOM-CORN SMUT. 393 
 
 No. 1048. Treatment same ; spores from surface of paper. At end of 24 hours only 
 a spore or two had germinated; at end of 48 hours a few more had germinated; at end 
 of 65 hours quite a few extra were beginning to germinate, though altogether not over 5 
 or 10 per cent. 
 
 No. 1050. Check. At end of 24 hours germination was abundant, though perhaps 
 exceeded in 1049. 
 
 No. 1051. In hot water 135 F. for 10 min.; spores from center of unbroken body. 
 At end of 24 hours examined and found the spores were germinating as well in all re- 
 spects as in check. The covering of the infected body had protected these central spores 
 so that they had not become wet, and the treatment if anything had done them good. 
 
 No. 1052. Treatment same ; spores from the same body but near the surface. These 
 spores had been wet by the water, and while their germination was retarded somewhat 
 and was not so abundant as the above, it was still quite vigorous. 
 
 No. 1053. Treatment same ; spores from surface of paper. At end of 24 hours less 
 than a dozen spores had germinated out of the many hundreds present. 
 
 No. 1054. Treatment same ; spores from inside a punctured body. At end of 24 
 hours did not find any germinating spores. Later on about a dozen germinating spores 
 were found. 
 
 No. 1055. Check. At end of 24 hours the spores had germinated very abundantly; 
 condition about as in 1051. 
 
 At end of four days the per cent, of germination in the above had not increased to 
 any appreciable extent. 
 
 No. 1103. In hot water 135 F. for 15 min.; spores from center of an unbroken 
 body. Examined at end of 24 hours and found the spores had begun to germinate 
 abundantly. 
 
 No. 1102. Treatment same; spores from surface of paper. None of these spores 
 germinated. 
 
 This experiment was tried twice with abwt the same results. A nutrient fluid was 
 used as the medium in this case. 
 
 No. 1107. In hot water 150 F. for 15 ,_iin., ipores from center of unbroken seed. 
 No spores germinated. 
 
 No. 1106. Treatment same; spores from . arfaceof paper. No spores germinated. 
 
 These experiments show that a short treatment with warm 
 water has no injurious effect, may possibly even be beneficial to 
 the germination of the spores. As the temperature of the water 
 is increased, however, it shows a retarding influence on the germi- 
 nation. Closely associated with retarded development is the fatal 
 effect of the hot water. In general, a direct exposure in water at 
 I30-I32 F. for five or ten minutes showed a retarding and with 
 some spores a fatal effect. A direct exposure for fifteen minutes 
 in water at 135 F. is almost certain to prove fatal to all of the 
 spores. Spores, however, in the unbroken bodies can stand 
 immersion in water of a higher temperature, the degree depend- 
 ing upon the thickness or impenetrability of the membrane to 
 the water. 
 
 It was shown in the treatment of broom-corn seed that an 
 exposure at 140 F. for fifteen minutes may be taken as the lower 
 limit at which we may begin to look for bad effects from the treat- 
 
394 BULLETIN NO. 47. [March, 
 
 ment of good seed. This gives a greater safety range than we 
 have in the similar treatment for the smut of oats or wheat. Per- 
 fect results in preventing the smut can not always be expected 
 with seed in which there are many unbroken infected kernels, 
 as the treatment (135 F. for fifteen minutes) will not be severe 
 enough to kill all of the spores, and subsequent handling may 
 break the kernels and scatter the spores among the seed. It is 
 quite possible, also, that spores that have worked down between 
 the glumes are sometimes protected sufficiently to withstand this 
 treatment and are able to infect the germinating plant. These 
 conditions probably account for the imperfect results obtained in 
 some of the following experiments where a large amount of smut 
 was mixed with the seed before treatment. 
 
 At the same time th'at the heat experiments were conducted a 
 few were tried to determine the influence of cold. Are the con- 
 ditions of winter weather such as would kill spores in infected 
 canes left outdoors on the ground ? The germination of some 
 spores that had been so treated was tried in the spring. Only one 
 trial was made but this failed to show any germinating spores. 
 However, they all presented the appearance as if they had germi- 
 nated before, which was quite likely the case. The germination 
 of spores subjected to the following conditions was also tried : 
 
 No. 1060. Spores on ice for 15 minutes. 
 
 No. 1061. Check culture. 
 
 No. 1062. Spores on ice for one hour. 
 
 No. 1063. Spores in ice-water for four hours. 
 At the end of 24 hours after placing in culture cells, all the 
 above had germinated abundantly, showing no difference at that 
 time or later. 
 
 Field experiments, 1894.. During this year experiments were 
 first undertaken to prevent broom-corn from smutting. Two lots 
 of seed, one ordinary seed and the other quite smutty, were di- 
 vided into three parts, a treatment with hot water and with a solu- 
 tion of copper sulphate being given to two of the parts of each 
 lot and the third parts left untreated. The seed, however, was 
 planted so late that the broom-corn did not have time to com- 
 pletely form its panicles before it was killed by frost. A care- 
 ful examination of the immature panicles that had appeared 
 showed but three smutted ones, and those all from the untreated 
 lot of badly smutted seed. In this plat one hundred twenty-five 
 plants were advanced enough to examine the panicles. The con- 
 ditions were not such as to give trustworthy results and no con- 
 clusions could be had. 
 
'897-1 
 
 BROOM-CORN SMUT. 
 
 395 
 
 Field experiments, 1895. This year the experiments were con- 
 siderably widened so as to include not only experiments in pre- 
 venting and increasing smut in the plants but also one to de- 
 termine whether plants could become infected by spores carried 
 to the tender parts above ground. The conditions and results of 
 these experiments are given in the table for 1895. From this it 
 will be seen that experiments i and 2 were conducted at Arcola, 
 111., which is in the principal broom-corn district of the state. 
 The seed, however, was planted on land that had not been in 
 broom-corn before. Unfortunately the broom-corn was cut a few 
 days before the writer examined it, but the smutted heads had 
 been left behind and so could be counted, while the total was 
 easily obtained from standing bases of the canes. The remaining 
 experiments were conducted at Urbana, 111., out of the broom- 
 corn district and on land that had never been in broom-corn be- 
 fore. In all cases the smut used was such that germinated readily 
 in water. In the last experiment the spores were in water that 
 was squirted on the young unrolled parts when the plants aver- 
 aged about six inches high. 
 
 FIELD EXPERIMENTS WITH BROOM-CORN SMUT, 1895. 
 
 No. 
 
 Conditions of the experiments. 
 
 Smutty. 
 
 Free. 
 
 Total. 
 
 % Smutty. 
 
 i. 
 
 Seed mixed with smut; no treat- 
 
 40 
 
 760 
 
 800 
 
 5. 
 
 
 
 
 
 
 
 2. 
 
 Seed mixed with smut ; treated with 
 hot water 135 F. for 15 min. At 
 Arcola 111 . 
 
 2 
 
 708 
 
 800 
 
 O.25 
 
 
 
 
 
 
 
 
 Ordinary seed ; no treatment 
 
 20 
 
 118^ 
 
 1 201 
 
 1.66 
 
 
 
 
 
 
 
 4- 
 
 Seed mixed with smut; no treatment. 
 
 126 
 
 1074 
 
 1 200 
 
 10.5 
 
 5- 
 
 Seed treated with hot water 135 F. 
 for 15 min.; mixed with smut two 
 years old 
 
 174 
 
 1072 
 
 1246 
 
 14. 
 
 6. 
 
 Seed mixed with smut; treated with 
 hot water 135 F. for 15 min 
 
 2 
 
 927 
 
 929 
 
 0.21 
 
 7- 
 
 Seed mixed with smut; treated with 
 hot water 140 F. for 15 min 
 
 I 
 
 1320 
 
 1321 
 
 0.07 
 
 8. 
 
 Seed mixed with smut; placed in 
 water to skim off smutted kernels; 
 treated with hot water 135 F. for 
 1 5 min 
 
 o 
 
 1168 
 
 fi 68 
 
 O. 
 
 
 
 
 
 
 
 9- 
 
 Seed treated with hot water 135 F. 
 for 15 min.; smut placed on young 
 plants soon after coming up 
 
 I 
 
 I3M 
 
 1315 
 
 0.07 
 
 These experiments show that in every case where used the 
 hot water practically prevented the smut, no matter whether ordi- 
 nary or very smutty seed had been so treated. Also that whereas 
 
396 BULLETIN NO. 47. [March, 
 
 the ordinary seed gave less than 2 per cent, of smutted plants, 
 this was. increased to 10 and 14 per cent, when very smutty seed 
 was used ; that smut two years old which had been kept in a dry 
 place had lost none of its power to infect plants. Lastly it was 
 shown that smut in these plants was not increased by spores being 
 placed on the young parts above ground. Before drawing con- 
 clusions from these experiments, the conclusions from which 
 seemed so evident, it was desired to repeat them another year, 
 and add others suggested by them. 
 
 Field experiments, 1896. The experiments this year were all 
 made at Urbana, the ground that had been used the year before 
 and a new piece being had for the two sets of experiments. 
 With the ground that had been in broom-corn the previous year, 
 the aim was two-fold. First, to determine the relation of smut in 
 the land to the amount of smut in the crop ; and second, to test 
 again the value of hot water treatment. 
 
 In table I for 1896 is given a diagram of the way the land was 
 platted during the two years. The dark lines indicate the boundary 
 of the land. In 1895 t^ e seven plats, 3-9, ran cross-wise, while in 
 1896 the four plats, a-d, extended lengthwise of the same. From 
 the table it will be seen that in 1895 plats 4 and 5 bore by far the 
 smuttiest crop ; but as most of the smutty panicles were removed 
 before much of the smut was shed, there was perhaps not much 
 that reached the ground in any plat. However, to make a differ- 
 ence, in the fall of 1895 a large amount of smut was dusted from 
 the panicles all over plat 4 and the smutted panicles were placed 
 on this plat. There could be no doubt that this plat contained a 
 good deal of smut and that at least plats 8 and 9 had very little if 
 any. If smut in the land was one of the means of infecting a 
 crop, then the plants in the four plats of 1896 might be expected 
 to show the most smut where they crossed plat 4 of 1895. In the 
 table the total number of stalks, the number of smutted ones, and 
 the per cent, of smutted ones that were found in the experiment 
 of 1896 are given for each of the areas formed by the cross plat- 
 ing of the two years. A glance at this will show that plat 4 in 
 none of the four treatments gave evidence of an increased per 
 cent, of smut over the rest of the land having seed treated the 
 same. This, taken with the fact that in plat a, where the seed was 
 treated and there was no smut in any of the areas, would indicate 
 that smutty land is not an important factor in producing a smutty 
 crop. 
 
 The second aim of the experiment, to determine the effect of 
 hot water treatment, is shown in the column of totals for the four 
 treatments. Ordinary seed treated with hot water gave a crop 
 
1897.} 
 
 BROOM-CORN SMUT. 
 
 397 
 
 
 
 * 
 
 co 
 
 
 
 ui 
 
 M mco 
 
 CO O CO 
 
 C>vO 4 
 
 O O 
 
 ui 
 
 3 
 
 rO PI P) 
 
 PI O 
 
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 ^- 2 
 
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 3- 
 
 
 
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 PI 
 
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 Panicles. 
 
 S t^C 
 
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 III 
 
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 S a " 
 
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 ^ *-* o 
 
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 entirely free from smut, while the crop from the same lot of seed 
 but not treated had nearly three and a half per cent, of the pani- 
 cles smutted. In the case where smut was mixed with the seed 
 
398 
 
 BULLETIN NO. 47. 
 
 [March, 
 
 the part that was afterward treated with hot water produced a crop 
 that only had four and one-third per cent, of the panicles smutted, 
 while the untreated part gave a crop of which twenty-eight per 
 cent, was smutted. The results of treatment, then, were the same 
 as in the previous year, save that in the case of the badly smutted 
 seed the prevention of smut was not quite so complete. This can 
 be explained on the assumption that the treatment was not severe 
 enough to kill all the spores (spores in the inside of smutted ker- 
 nels or possibly some of those that had slipped down between the 
 glumes of sound seed) and by the fact that here it was an unusu- 
 ally good year for the development of smut, as is shown by the 
 large amount given for the plats of these and the next experiments. 
 The second set of experiments made in 1896, as was stated, 
 was on land that had never before been in broom-corn, and 
 included beside the preventive experiments (as a check on the 
 preceding set) a few to determine the possibility of infecting 
 young plants of different ages by placing spores on them. The 
 results are embodied in the following table. 
 
 TABLE 2. FIELD EXPERIMENTS WITH BROOM-CORN, 1896. 
 
 Plat. 
 
 Conditions of the experiments. 
 
 Smutty. 
 
 Free. 
 
 Total. 
 
 Per cent. 
 
 A. 
 
 Ordinary seed ; treated with hot 
 water I33-I35 F. for 15 min. . . . 
 
 2 
 
 i675 
 
 1677 
 
 0.12 
 
 B. 
 
 Seed mixed with smut; treated with 
 
 360 
 
 1128 
 
 1488 
 
 24. 
 
 
 
 
 
 
 
 c 
 
 
 ic? 
 
 in ^6 
 
 iSO^ 
 
 IO. 
 
 
 
 
 
 
 
 D. 
 
 Seed mixed with smut; no treatment. 
 
 495 
 
 565 
 
 1050 
 
 47- 
 
 E. 
 
 Seed treated with hot water 133- 
 135 F. for 15 min.; smut placed 
 on young plants before appearing 
 above ground 
 
 3 
 
 106 
 
 114 
 
 7- 
 
 F* 
 
 Seed treated with hot water 133- 
 135 F. for 15 min.; smut placed 
 on young plants just after appear- 
 ing above ground .... 
 
 I 
 
 345 
 
 346 
 
 o.^ 
 
 
 
 
 
 
 
 G.* 
 
 Seed treated with hot water 133- 
 135 F. for 15 min.; smut placed 
 on plants when about two feet 
 high. 
 
 o 
 
 420 
 
 420 
 
 o. 
 
 Hf 
 
 Quite smutty seed of the season of 
 1893 
 
 509 
 
 481 
 
 990 
 
 51. 
 
 Examination of this table shows that hot water treatment of 
 ordinary seed has again given the uniform result of the preven- 
 
 * Seed of all the plants was planted May 27. Smut in water was squirted on the 
 young unrolled parts of the plants in plat F. on June 13, while in plat G. the same opera- 
 tion was performed on July o,. 
 
 t A different variety of broom-corn seed than that used in any other experiment in 
 1895 or 1896, but from the same lot of seed as was used in 1894. 
 
BROOM-CORN SMUT. 399 
 
 tion of smut. The same seed untreated gave an unusually large 
 number of smutted plants, nineteen per cent. With the seed 
 mixed with smut the treated part showed less favorable results 
 than in any of the previous similar experiments, but still there is 
 a very decided difference between it and the untreated part, which 
 had over fifty per cent., or twice as much. The placing of smut 
 on very young plants before they came above the ground gave 
 rise to a few smutty plants, but the percentage was not nearly so 
 great as it would have been had the smut been placed on seeds 
 instead. Placing smut on the young parts after the plants had ap- 
 peared above the ground gave results similar to a previous experi- 
 ment no increase in smut. 
 
 The results of the three years are thus seen to be quite uniform, 
 always showing favorable for the treatment. The only seeming 
 exception is in the case of treatment of very badly smutted 
 seed. Here the treatment was not severe enough to kill all of the 
 smut spores, and the varying favorable conditions of the different 
 years or ground used gave rise to a varying amount of smut, 
 though never to nearly so great a per cent, as in the same seed 
 untreated. 
 
 Prevention experiments elsewhere. In the literature of the 
 smuts of the sorghum group of plants the only prevention experi- 
 ments we have come across are those conducted in 1891 by 
 Kellerman at the Experiment Station of Kansas. With Ustilago 
 Sorghi of sorghum he tried seed treatment with different strengths 
 of solution and time of immersion of potassium sulphid and chlo- 
 rid of iron, and also with hot water. The check plats gave such 
 a small per cent, of smutted plants that the author drew no con- 
 clusions from the results of his experiments. In the two cases 
 where he used hot water, however, he had no smutted plants. It 
 is stated that at the Khandesh Experiment Farm, 1 of India, season 
 of 1892, copper sulphate treatment of seed was used with good 
 results in preventing a common smut of sorghum. 
 
 EFFECT OF ENVIRONMENT ON PARASITE AND HOST. 
 
 Some interrogations. What are the environmental conditions 
 favorable or unfavorable for the infection of a plant by the smut 
 and for the development of the latter afterward ? Such conditions 
 may be quite general or quite specific. Some years or certain 
 localities give rise to badly smutted crops and we say the general 
 conditions have been favorable for such and usually ascribe such 
 conditions to the presence of spores with the seeds and to the 
 
 'Exp. Stat. Rec. 5: 354. 
 
400 BULLETIN NO. 47. [March, 
 
 warm moist weather at the infection period. But there are other 
 more specific, perhaps largely indeterminable, conditions than 
 these that might have an influence in determining the percent, of 
 smut that appears in the plants. Take, for instance, very smutty 
 seed ; why does it in two succeeding years in the same locality 
 show the variation from ten (plat 4/95) to forty-seven (plat D, '96) 
 per cent.? Given the same ordinary seed planted but a few days 
 apart on plats but a short distance from each other; why does it 
 show the variation from three (plat c, '96) to nineteen (plat C, '96} 
 per cent.? In 1894 smutty seed a year old was planted so late that 
 the plants showed but a few immature panicles before they were 
 killed by the frost. A careful examination for smut in the one 
 hundred and twenty-five panicles that appeared gave three with 
 evidence of smut. The same lot of seed planted at the proper 
 time in 1896 gave over fifty (plat H, '96) per cent, of smutted pani- 
 cles. What were the causes of this difference ? Or to make the 
 case extremely specific in the same lot of seed in the same plat 
 we have one stalk smutted and another free. Why? 
 
 Environment before infection. While we are not able now to 
 cite each case to its cause or causes, yet we may give certain con- 
 ditions that seem to have a greater or less bearing. Such fall into 
 two groups ; namely, those that are favorable or unfavorable to 
 infection of the host by the fungus, and those that affect the rela- 
 tionship of the two after infection. Take two seeds, for instance, 
 and the soil immediately surrounding each. One or more of the 
 following differences in condition might determine why one 
 became infected and the other not : number and germinative charac- 
 ter of the spores present; amount of water present; character of 
 the gases in the soil and water ; chemical character of the soluble 
 parts of the soil ; bacterial development as unfavorable for pro- 
 lific germination of spores ; nutrient solutions formed from manure 
 and decayed vegetable matter as a source for prolific formation of 
 sporidia ; movement of water as a means of bringing germs to 
 infection-area of the germinating seed ; heat in the presence and 
 absence of moisture. Or the conditions of the seeds themselves 
 possibly might aid in deciding the matter; namely, age of seed 
 as affecting character and vitality of germination and these in turn 
 favorable or not for the germs present; individual character or 
 vitality of different seeds; heat and moisture as affecting rapidity 
 of germination and character of tissue formed ; depth of planting, 
 etc. as affecting length and character of epicotyl and leaf-sheath. 
 
 Environment after infection. Brefeld has shown that certain 
 smuts sometimes succeed in entering their host but still do not 
 succeed in forming spores. In the case at hand the fungus sue- 
 
1897.} BROOM-CORN SMUT. 4OI 
 
 ceeds in entering the germinating plantlet say in June, while the 
 spore masses do not become visible in the flower parts of the 
 same until between two and three months later. May there not 
 be conditions developed during this time that are favorable to the 
 one and not to the other? May not outside conditions of heat 
 and moisture or peculiar hereditary character of individual plants 
 favor the formation of plant tissue having great resistance to the 
 penetrating threads of the fungus, thus conquering it, or the 
 reverse? May not the growing point of the plant outstrip in up- 
 ward growth the fungous threads and thus cut them off from 
 further development? Would not tardy invasion of the floral 
 parts prevent or lessen the spore formation ? This latter question 
 can be answered in the affirmative, if we count the evidence pre- 
 sented by flowers with more or less of their parts infected or of 
 panicles with only part of the flowers infected, apparently the 
 earlier developed being free. Such conditions and results are, how- 
 ever, with our present knowledge largely matters of speculation. 
 
 HISTORICAL REVIEW. 
 
 Bibliography. The following list includes all of the articles 
 that the writer has been able to find in which mention of this 
 smut is made. The references are reported by the name of the 
 fungus used rather than by the general title of the article, except 
 when the article especially treats of the fungus. 
 
 BARY, A. de. Ustilago Tulasnei. Vergleich. Morph. u. Biol. der Pilze Mycet. u. 
 Bact. 369. 1884. 
 
 Gives Liebenberg as authority for germination of spores after being in her- 
 barium six and a half years. 
 BESSEY, C. E. Ustilago Sorghi (Link) Pass. Neb. Farmer 14: 189. 6 Mr. 1890. 
 
 Notes its appearance in Nebraska, and recommends blue-vitriol treatment of 
 seed. 
 
 BREFELD, O. Ustilago Tulasnei Kiihn auf Sorghum -vulgar e. Untersuch. aus dem 
 Gesammt. der Mykol. 12: 120-122. pi. j.f. iq-22. 1895. 
 
 Gives culture experiments, etc. with this fungus. 
 BURRII.L,T. J. Ustilago Sorghi (Link) Winter. Proc. Am. Soc. Micr. 1888: (12). 
 
 Lists this smut from Illinois. 
 COMES, O. Ustilago Tulasnei Kiihn. Crittog. Agr. 75. 1891. 
 
 Gives brief note as to hosts, etc. 
 DE-ToNI, J. B. Ustilago Sorghi (Link) Pass. Syll. Fung. 7 s : 456. 28 O. 1888. 
 
 Gives description, hosts, synonyms, etc. 
 EVANS, W. H. Sorghum Smuts. Handb. Exp. Stat. Work. 326. 1893. 
 
 Gives a brief note on U. sorghi. 
 
 FAILYER, G. H., and WILLARD, J. T. Smut in Sorghum. Exp. Stat. Kans. St. Agr. 
 Coll. 16: 145. 1891. 
 
 Mention finding two kinds of Miiut on inmost d varieties of sorghum. 
 
402 BULLETIN NO. 47. March, 
 
 FARLOW, W. G., and SEYMOUR, A. B. Ustilago Sorghi (Lk.) Pass. Prov. Host-Index 
 Fungi U. S. 154. Je. 1891. 
 
 Give as hosts Sorghum saccharatum and S. vulgare. 
 
 FISCHER DE WALDHEIM, A. Tilletia Sorghi-vulgaris,T\\\. Pringsh. Jahrb. 7 : 106, 
 in. 1869. (Transl. N. Y. St. Agr. Soc. 1870: 280. 1871.) 
 Lists this fungus. 
 
 FISCHER DE WALDHEIM, A. Ustilago Tulasnei, Kiihn. Aper9u System, des Ustil. 
 12. 1877. (Hedw. 16: 101. Jl. 1877.) 
 
 Gives brief description with synonyms. 
 FRANK, A. B. Ustilago Tulasnei, Kiihn. Die Krankh. der Pflanz. 431. iSSo. 
 
 Gives brief description, distribution, etc. 
 FRIES, E. Sporisorium Sorghi. Syst. Mycol. 3: 454-5. 1832. 
 
 Gives botanical description of the fungus copied from Link. 
 
 KELLERMAN, W. A., and SWINGLE, W. T. Notes on Sorghum Smuts. Proc. Kans' 
 Acad. Sci. 12: 158. 1890. 
 
 Note distribution of Ustilago Sorghi in U. S. and give hosts in Kansas. 
 KELLERMAN, W. A. Experiments with Sorghum Smuts. Exp. Stat. Kans. St. Agr. 
 Coll. 23: 95-101. //. 2. Ag. 1891. 
 
 Gives descriptions of U. Sorghi and U. Reiliana and results of infection and 
 prevention experiments. 
 
 KUHN, J. Die Brandformen der Sorghum-Arten, Tilletia Sorghi, Tul. and Ustilago 
 cruenta, Kiihn. Hamb. Gart. u. Blumenzeit. 28: 1778. 1872. 
 
 Briefly discusses the two forms, of which U. cruenta is described as new. 
 
 KUHN, J. Ustilago Tulasnei, Kiihn. Sitz. nat. Ges. Halle 1874. (Bot. Zeit. 32: 122. 
 20 F. 1874.) 
 
 States that germination, etc. shows the fungus to be an Ustilago rather than 
 a Tilletia. 
 
 KUHN, J. Die Brandformen der Sorghumarten. Mittheil. d. Vereins f. Erdkumlf. 
 1877. (Hedw. 17: 6-14. Ja. 1878.) 
 
 Gives differences between the smuts so far found on Sorghum, of which U. 
 Tulasnei is named as one. 
 LINK, H. F. Sporisorium Sorghi. Linn. Sp. Plant. 6 s : 86. 1825. [ed. Willd.] 
 
 Describes a specimen from Egypt on Sorghum rulgare, being the first printed 
 account of our fungus. 
 LUERSSEN, C. Ustilago Tulasnei, Kiihn. Handb. der System. Bot. 1: 250. 1879. 
 
 Gives brief specific characters. 
 
 NORTON, J. B. S. Ustilago Sorghi (Link) Pass. Trans. Acad. Sci. St. Louis 7: 231. 
 pi. 2 5 .f. /-j. 9 N. 1896. 
 
 Gives note on germination. 
 OUDEMANS, C. A. J. A. Tilletia Sorghi, Tull. Archiv. Neerl. 8: 381. 1873. 
 
 Notes the finding of this at Utrecht in 1871. 
 
 PRILLIEUX, E. Ustilago Sorghi (Lk.) Pass. Bull. Soc. Bot. France 42: 36-39, /. a-e. 
 Ja. 1895. 
 
 Gives structural details of infected body. 
 RABENHORST, L. Tilletia Sorghi, Tul. Hedw. 10: 18. 1871. 
 
 Notes the collection of the fungus at Kurdistan in the orient. 
 
 SCHROETER, J. Ustilago Sorghi (Link). Krypt. Flora v. Schlesien 3 1 : 267. 1889. 
 Gives description and synonyms. 
 
7<?P7-1 BROOM-CORN SMUT. 403 
 
 SORAUEK, P. Tilletia Sorghi vulgar is. Handb. Pflanzenkrankh. 259. 1874 
 
 Makes allusion to this fungus. 
 THUMEN, F. de. Ustilago Sorghi, Pass. Hedw. 12: 114. Ag. 1873. 
 
 Gives description of this as a new species with Passerini as the authority. 
 TRELEASE, W. Ustilago Sorghi (Link). Trans. Wis. Acad. Sci. Arts. Letters 6: 
 1886. (Prelim. List Par. Fungi Wis. 34. N. 1884. 
 
 Notes distribution of the fungus in America. 
 
 TULASNE, L. R. Tilletia Sorghi-vulgaris. Ann. Sci. Nat. Bot. III. 7: 116. /. j. 
 f. 17-22. 1847. 
 
 Describes this species under above name. 
 
 WEBBER, H. J. Ustilago Sorghi (Link) Pass. Agr. Exp. Stat. Neb. I 9 : 69. 18 D. 1889. 
 (Ann. Rep. Neb. St. Bd. Agr. 1889: 214. 1890.) 
 
 Notes occurrence of this fungus in Nebraska. 
 WINTER, G. Ustilago Sorghi (Link). Rabenh. Krypt. Flora 1: 90. 1884. [and ed.] 
 
 Gives specific description, synonyms, etc. 
 
 Exsiccati. Specimens of the fungus have been distributed 
 under the following names in the quoted exsiccati. 
 
 Ustilago Sorghi, Pass. Thiimen Herbarium mycologicum ceconomicum 63. 1873. 
 Ustilago Tulasnei, K'uhn. Rabenhorst Fungi Europaei 7997. 1875? 
 Ustilago Sorghi (Lk.) Wint. Ellis North American Fungi 1496. 1885. 
 Ustilago Sorghi (Lk.). Briosi & Cavara Funghi parassiti delle piante coltivate od 
 utile 28. 1889. 
 
 Ustilago Sorghi (Link) Wint. Roumeguere Fungi selecti exsiccati 5128. 1890. 
 
 Nomenclattire. So far as can be gathered from the preced- 
 ing references the history of the fungus is as follows: In 1825 
 Link published under the name of Sporisorittm Sorghi a smut on a 
 variety of sorghum gathered in Egypt and communicated by 
 Ehrenberg. The fact that the description given is not minute and 
 the further fact that several smuts have since been found on the 
 same host tend to make it uncertain whether this description 
 refers to what is now commonly called Ustilago Sorghi or not. 
 This uncertainty, however, is dispelled by the existence of the 
 original specimen in the Berlin Herbarium, where it was examined 
 by Ktihn and found to be this fungus. The next reference to this 
 species that could be found, aside from the copied description of 
 Link by Fries in 1832, is under the title of Tilletia Sorghi-vulgaris 
 by Tulasne in 1847. This specific name has been abbreviated by 
 some authors into Tilletia Sorghi. In 1874, however, Kiihn 
 showed that the germination of this fungus put it in the genus 
 Ustilago rather than Tilletia, and he renamed it Ustilago Tulasnei. 
 In the meantime, in 1873, another supposedly new species of smut 
 on sorghum was described under the name of Ustilago Sorghi. 
 Although issued by de Thiimen in his exsiccati and described by him 
 in Hedwigia, he gave Passerini, the collector, as authority for the 
 name. Fischer de Waldheim in 1877 placed this name as a syno- 
 nym of U. Tulasnei, thus regarding the former fungus as not 
 
404 BULLETIN NO. 47. [March, 
 
 distinct. Winter (in Die Pilze) seems to have been the first to 
 have placed the smut in the genus Ustilago and at the same time 
 to have used the earliest specific name applied and the authority, 
 namely, Ustilago Sorghi (Link), for the same. 
 
 However, our study of the reproduction of the fungus shows 
 it to be a Cintractia. This would make the present name Cin- 
 tractia Sorghi but for the fact that De-Toni has already referred 
 the Sorokine fungus (Endothlaspis Sorghi) questioningly to this 
 genus as Cintractia ? Sorghi (Sorok.), thus making a fungus already 
 of that name. So far as we can learn the identity of this latter 
 fungus has not yet been further worked out, either as to its 
 generic position or its relationship to the smuts already reported 
 on the sorghum-like plants ; yet from what we can gather from 
 the anatomical description and figures given by Sorokine it agrees 
 in general with our fungus, thus increasing the belief that it is a 
 Cintractia. To avoid confusion with the species of Sorokine, 
 however, we present the second specific name applied to the fun- 
 gus we are considering, the name used by Tulasne, which gives 
 the following arrangement, Cintractia Sorghi-vulgaris (Tul.). 
 
 SUMMARY. 
 
 1. Broom-corn smut is a parasite belonging to the lowest 
 group of plants called fungi. On the plants very closely related 
 to broom-corn this and several other smuts have been found. As 
 is shown by its spore formation, this smut really belongs to the 
 genus Cintractia rather than to Ustilago, to which it has of late 
 years been referred, and Cintraciia Sorghi-vulgaris (Tul.) is the 
 name suggested for it. 
 
 2. Broom-corn infected \vith this fungus produces, as a usual 
 thing, brush of a very i.iferior quality, the rays being scattered 
 on a large central axis instead of having a common point of ori- 
 gin. Seed formation is also prevented by the fungus forming 
 its spores in the young ovaries and stamens. Brush gathered with 
 moisture on it may have these spores settle in this and stick to 
 the brush when it dries, thus affecting its appearance. The 
 thrashing of infected brush is disagreeable because of the dust 
 formed by the fungous spores. 
 
 3. Broom-corn only becomes successfully infected by the 
 fungus while the seeds germinate. The fungus succeeds at that 
 time in penetrating the very young tissues usually before the 
 plant issues above the ground, and the fungous threads which 
 have thus gained entrance increase in amount, and eventually 
 closely follow the upward growth of the stem during the whole 
 
7^7-] BROOM-CORN SMUT. 405 
 
 season. When this is about completed and the plant begins to 
 develop its reproductive parts, the fungous threads become abun- 
 dant just beneath the epidermis of the ovary and the stamens. This 
 mass soon loses its identity as threads by the gelatinization of 
 the cell walls and by the re-arrangement of cell contents. From 
 this fertile stratum the spores are developed centripetally. Thus 
 when the panicles appear we find their stamens and ovaries con- 
 verted into seed-like bodies filled with a dusty mass of spores. 
 These spores, if placed immediately in water, will germinate read- 
 ily, a condition that also holds true for those that are a number of 
 years old. 
 
 4. Experiments showed that the amount of smut ordinarily 
 occurring in broom-corn can be greatly increased by mixing a lib- 
 eral supply of smut with the seed before planting, but was not in- 
 creased by planting seed in land that had smut in it or by placing 
 smut on the plants after they appeared above ground. 
 
 5. These experiments show that the way to prevent smut is 
 to use seed free from it or seed whose attached smut germs have 
 been killed. This killing was accomplished by treating seed with 
 hot water, 135 F., for ten to fifteen minutes. Ordinary seed 
 that gave with check experiments from two to nearly twenty per 
 cent, of smutted plants, when treated, gave plants free from the 
 smut. Seed mixed with abundance of smut, when treated, pro- 
 duced plants while not always free from smut at least always with 
 a much smaller per cent, of infected ones than similar seed not 
 treated. 
 
 PREVENTION OF BROOM-CORN SMUT. 
 
 For the convenience of those who may wish to try the hot 
 water treatment for the prevention of smut in their broom-corn, 
 the following method of procedure is suggested. The station will 
 be pleased to receive information as to the success of those who 
 may try this, also any suggestions for improvement that use may 
 bring out. 
 
 Advisability. From the experiments conducted it is seen 
 that smut of broom-corn can be prevented or at least decidedly 
 lessened in amount. It then becomes merely a question with each 
 grower to decide whether or not the injury done to his crop dur- 
 ing various years is sufficiently great to warrant the treatment. 
 From the opinions heard expressed on this matter, it would seem 
 that most broom-corn raisers think that methods favorable to the 
 prevention of smut are desired. Beside the hot water treatment 
 selection of seed free from smut is a means to the same end, and 
 one that is generally recognized, although the reason is not al- 
 
406 BULLETIN NO. 47. [March, 
 
 ways so clearly understood. In either case it is to have the seeds 
 free from living germs of the fungus when germination takes 
 place, as that alone is the time when the smut germ can success- 
 fully infect the plant. Selection of seed, however, unless one 
 knows all about its history, is not safe, as by mere examination 
 one can not tell whether or not it has spores present, unless it is 
 rendered quite smutty. Hot water treatment, on the other hand, 
 is surer and involves no cost save the labor of treatment. As the 
 amount of broom-corn required to seed an acre is comparatively 
 small the treatment is not nearly so tedious as is the quite similar 
 operation with oats. 
 
 Hot water method. The following is recommended as a 
 method of treatment, mechanical details of which can be changed 
 to suit the convenience of the operator. A reliable thermometer 
 and two vessels of hot water (one at a temperature of about 135 
 F., and the other at 135 F. with means for keeping it there either 
 by fire, additional hot water or injection of steam) are needed for 
 the operation. The seed to be treated to the amount of a bushel 
 or less is placed in a coarse bag which is immersed in the first ves- 
 sel and then raised up and down until the seed has come to about 
 the temperature of the water. This should be quickly accom- 
 plished and is done so that the temperature of the second vessel 
 will not be lowered when the bag is placed in it. This is now 
 done, and the temperature, as shown by the thermometer placed 
 among the seeds, should be kept near 135 F. If this tempera- 
 ture is allowed to go up any the seed is in danger of being injured, 
 and if it goes down much the spores may not all be killed. After 
 being ten to fifteen minutes in the second vessel, the seed is re- 
 moved and dried, when it is then ready for planting. While it is 
 not advisable ever to use very smutty seed, if such is used, most 
 of the smutted kernels may be removed by immersion and stir- 
 ring in water and then skimming off the floating ones. A good 
 many perfect seeds, however, are apt to be lost by this operation, 
 as not all of the sound ones sink. Hot water treatment should 
 then be given the seed. 
 
 G. P. CLINTON, M. S. 
 
 Assistant Botanist. 
 
 EXPLANATION OF ILLUSTRATIONS. 
 
 Plate I. The upper engraving shows the brush from a plat of broom-corn whose 
 seed was mixed with smut and then planted. Over ten per cent, of the plants were 
 infected. The lower engraving shows the brush from a plat whose seed was mixed with 
 smut and then treated with hot water at 140 for 15 minutes. But one stalk of the 1321 
 .stalks in this plat was infected. 
 
BROOM-CORN SMUT. 407 
 
 Plate II. Upper left hand engraving shows slightly enlarged smutted flowers of 
 broom-corn. Upper right hand engraving shows panicles of broom-corn ; the right one 
 was free, and the other two were infected, the action of the fungus manifesting itself in 
 the enlarged central axes. The lower engraving shows at the right a free and at the left 
 an infected panicle. 
 
 Plate III. This shows details of spore infected parts of broom-corn. Figs, i-io 
 are magnified 4 or 5 diameters, figs. 11-13 about 10 diameters, fig. 14 about 250 diameters, 
 figs. 15-16 about 500 diameters. 
 
 Figs. 1-9 show infected parts of flowers, a. stamens, b. pistil, c. scales. In 
 I mycelium was found ; in 2 spores were beginning to be formed ; in 3 stamens were free 
 from mycelium and spore formation had just begun at apex of pistil ; in 4 stamens and 
 pistil were both infected but free from each other ; in 5 the infected parts were blended 
 together ; in 6 stamens and pistil merely showed distinct at apex ; 7-8 show rare forms 
 where all of the flower parts were infected ; 9 shows usual method of infection with 
 glumes free; 10 shows an drdinary uninfected seed enclosed in the glumes. Figs. 1113 
 show cross-sections through an infected body, a. false-membrane, b. mature spores, b 1 . 
 immature spores, c. columella. Fig. n represents section through apex, 12 through 
 center, and 13 through base of the infected body which is composed of pistil and sta- 
 mens. Fig. 14 shows cross-section through base of a rather young infected body, a. 
 representing false membrane composed of epidermal cells and sterile fungous threads, b. 
 mature spores, b. 1 immature spores, c. columella. Figs. 15-16 show more highly mag- 
 nified sterile fungous cells (a.) and spores (b.), fig. 15 being drawn from smut on im- 
 ported Chinese variety of sorghum, and 16 from broom-corn. 
 
 Plate IV. This shows the mycelium of the smut in the tissues of broom-corn. Fig. 
 i magnified about 150 diameters, and Figs. 2-6 about 500 diameters. 
 
 Fig. i shows a cross-section through the epicotyl of germinating broom-corn, near 
 union of epicotyl and leaf- sheath, a. representing mycelium, b. epidermis, c. parenchy- 
 matous cells of cortex, d. woody cells of central cylinder. Fig. 2. A more highly mag- 
 nified part of i. This shows condition of mycelium about three weeks after spores were 
 placed on seed. Fig. 3. Section through leaf near juncture of leaf-sheath and epicotyl, 
 showing narrowing of mycelium in the epidermal cell where entrance was probably 
 gained to the leaf. The leaf-sheath had been removed and spores placed on base of the 
 exposed young leaf. Figs. 4-4'. Mycelium in pith cells of a mature plant, 4 from base 
 of stalk and 4 1 from apex near panicle. Fig. 5. Mycelium in pith cells from top of 
 stalk at time flowers are being formed. Fig. 6. Mycelium in pith cells 46 days after 
 spores were placed on the seed. 
 
 Plate V. This shows germination of spores of broom-corn smut, a. representing 
 spores, b. pro-mycelium, b 1 . abstricted portions of pro-mycelium, c. sporidia and second- 
 ary sporidia, c. 1 germinating sporidia. Magnified about 500 diameters. 
 
 Fig. I. Germination of spores in distilled water, i at end of 6 hours, 2 at end of 
 9 hours, and 3 at end of 24 hours. Fig. 2. Germination of spores in distilled water at 
 end of 24 hours, showing origin of knee-joints and infection threads. Fig. 3. Germi- 
 nation of Kansas spores in distilled water. Fig. 4. Germination in distilled water of 
 spores taken from inside of seed that had been soaked in hot water at 130 F. for 5 min. 
 These spores probably germinated in contact with air. Fig. 5. Germination at end of 
 several days in a cell with only a film of water covering the spores. Figs. 6-8. Germ- 
 ination of spores in different fluids, 6 in distilled water, 7 in tomato-broth, 8 in beef- 
 broth, this last showing only the condition of the sporidia. Figs. 9-11. Germination 
 of spores in beef-broth. 9 at end of 19 hours, 10 at end of 22 hours, and n at end of 40 
 hours. 
 
408 
 
 BULLETIN NO. 47. 
 
 \March, 
 
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