I ^DEPARTMENT OF AGRICULTURE. 
 
 • pf3 BDREAD OF PLANT INDUSTRY -BULLETIN- No. 63. 
 
 INVESTIGATIONS OF RUSTS. 
 
 MARK ALFRED CAB 
 Cerealist in Charge of Cerea 
 
 VEGETABLE PATHOLOGICAL AND 
 INVESTIGATIONS 
 
 [SSOED JuiT 12, 1004. 
 
 DOCUMEN "' 
 
 
 ' 
 
 WASHINGTON: 
 
 GO\ EURNMKNT PRINTING oi'ih r;. 
 
BULLETINS OF THE BUREAU OF PLANT INDUSTRY. 
 
 The Bureau of Plant Industry, which was organized July 1, 1901, includes Vege- 
 table Pathological and Physiological Investigations, Botanical Investigations and 
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 publications should, therefore, be made to (be Superintendent of Documents, Gov-! 
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 No. 1. The Relation of Lime and Magnesia to Plant Growth. 1901. Price, 10 cents. 
 
 2. Spermatogenesis and Fecundation of Zamia. 1901. Price, 20 cents. 
 
 3. Macaroni Wheats. 1901. Price, 20 cents. 
 
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 5. Seeds and Plants Imported. Inventory No. 9. 1902. Price, 10 cents. 
 
 6. A List of American Varieties of Peppers. 1902. Price, 10 cents. 
 
 7. The Algerian Durum Wheats. 1902. Price, 15 cents. 
 
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 9. The North American Species of Spartina. 1902. Price, 10 cents. 
 
 10. Records of Seed Distribution and Cooperative Experiments with ( trasses and 
 
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 13. Experiments in Range Improvement in Central Texas. 1902. Price, 10 
 
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 14. The Decay of Timber and Methods of Preventing It. 1902. Price, 55 cents! 
 
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 16. A Preliminary Study of the Germination of the spores of Agaricus Campes- 
 
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 [Continued on page :> of cover.] 
 
Bui 63, Bureau of Plant Industry, U. S Dept of Agriculture. 
 
 Plate 
 
 A Perennial Rust. 
 (/tciDiuM Tuberculatum E.& K.on Calurrhoe involucrata Gr.) 
 
U. S. DEPARTMENT ( >F AGRICI I.I URE 
 
 BUKKM 101 PLANT INDUSTRY BULLETIN 
 
 IS. T. I. \ I.I.I )\\ A I 
 
 NVESTIGATIONS OK RUSTS. 
 
 MARK ALFRED CARLETON, 
 
 ( erealist in Charge of Cereal [nvestigations. 
 
 ' I .K.TABLE PATHOLOGICAL AND PHYSIOLOGY 
 INVESTIGATIONS. 
 
 u July 12, L904. 
 
 WASHINGTON: 
 
 Q( '\ ERNMENT PRINTING I >FFI< H 
 I 9 Or! 
 
BUREAU OF PLANT INDUSTRY. 
 
 B. T. Galloway. Chief. 
 J. E. Rockwell, Editor. 
 
 VEGETABLE PATHOLOGICAL AND PHYSIOLOGICAL INVESTIGATIONS. 
 
 SCIENTIFIC STAFF. 
 
 Albert F. Woods, Pathologist and Physiologist. 
 
 Erwin F. Smith, Pathologist in Charge of Laboratory of Plant Pathology. 
 
 George T. Moore, Physiologist in Charge of Laboratory of Plant Physiology. 
 
 Herbert J. Webber, Physiologist in Charge of Laboratory of Plant Breeding. 
 
 Walter T. Swingle, Physiologist in Charge of Laboratory of Plant Life History. 
 
 Newton B. Pierce, Pathologist in Charge of 1'acijie Coast Laboratory. 
 
 M. B. WAITE, Pathologist in Charge of Ineestigatious of Diseases of Orchard Emits. 
 
 Mark Alfred Carleton, Cerealistin Charge of Cereal Investigations 
 
 Hermann von Schrenk," In Charge of Mississippi Valley Laboratory. 
 
 P. H. Rolfs, Pathologist in Charge of Subtropical Laboratory. 
 
 C. 0. TowNSEND, Pathologist in Charge if Sugar fleet [mestigatiotts. 
 
 P. H. Dorsett, Pathologist. 
 
 Rodney H. Tuff.,'' Physiologist. 
 
 T. II. Kearney, Physiologist, Plant Breeding. 
 
 Cornelius L. Shear, Pathologist. 
 
 William A. Orton, Pathologist. 
 
 W. M. Scott, Pathologist. 
 
 Joseph S. Chamberlain, Physiological Chemist, Cereal Investigations. 
 
 II. E. B. McKenney, Physiologist. 
 
 Flora W. Patterson, Mycologist. 
 
 Charles I'. Hartley, Assistant in Physiology, Plant Breeding. 
 
 Karl F. Kellerman, Assistant in Physiology. 
 
 Deane B. Swingle, Assistant in Pathology. 
 
 A. W. Edson, Scientific Assistant, Plant Breeding. 
 
 Jesse P>. Norton, Assistant in Physiology, Plant Breeding. 
 
 James B. Rorer, Assistant in Pathology. 
 
 Ll.oYU S. TENNY, Assistant in I'a/hologg. 
 
 George <;. Hedgcock, Assistant in Pathology. 
 
 PERLEY SPAULDING, Scientific Assistant. 
 I'. J. O'GARA, Scientific Assistant. 
 
 A. I>. Shamel, Scientific Assistant, Plant Breeding. 
 
 T. Ralph Robinson, Scientific Assistant, Plant Physiology. 
 
 Florence Hedges, Scientific Assistant, Bacteriology. 
 
 Charles J. Brand, Scientific Assistant in Physiology, Plant Lift History. 
 
 a Detailed to the Bureau of Forestry. 
 
 b Detailed to Botanical Investigations and Experiments. 
 
\.l\ 
 
 fRANSMITTAL 
 
 I S I > I I- \ i; ;'i'\ii \ I i ii A.GKICULTURJ . 
 
 Bi re \i of Plant Lndi str^ . 
 
 ( )ril('K OF THE ( II 1K1'. 
 
 Waxkiw/ton, D. < .. April iO, /!'"',. 
 Sir: I have the honor to transmit herewith the manuscript of ;i 
 technical paper entitled "Investigations of Rusts," by .Mark Alfred 
 Carleton, Cerealist in Charge of Cereal Investigations, Vegetable 
 Pathological and Physiological Investigations, and recommend its 
 publication as Bulletin No. 63 of the series of this Bureau. 
 
 The two illustrations accompanying the manuscript are neccssar}' 
 to a complete understanding of the subject-matter of this paper. 
 Respectfully, 
 
 B. T. Galloway, 
 
 ( 'hief of />'"/■' '"/. 
 
 1 Ion. .1 \MI .» W I In in. 
 
 >'. ./■, tii, y ,,/ . \.(jricultit)\ . 
 
 3 
 
Digitized by the Internet Archive 
 in 2013 
 
 http://archive.org/details/investofOOunit 
 
PRKFACE. 
 
 The experiments and oiisciv.iii i nists which arc the basis of 
 
 the following notes were begun by Mr. Carleton several years ago, 
 ami ucic continued at intervals until the spring of L900, when the 
 pressure of other duties prevented further work of this kind up to 
 the presenl time. The results obtained in many instances are slill 
 incomplete, bul are of sufficient value to be recorded. Some of the 
 species studied arc of much economic importance. The investigation 
 i- a continuation of the work reported in Bulletin !•'> of the l>i\ ision 
 of Vegetable Physiology and Pathology, and is concerned chiefly with 
 the segregation of rusl forms of economic importance on the common 
 
 grasses and tin mpletion of the life history of certain species. The 
 
 work is to be carried on more extensively during 190-1. 
 
 A. P. Woods, 
 PnthoJoqixt and Phyxloloqixt. 
 Office of Vegetable Pattiologn m \\i> 
 
 Physiological Inn esi ig \th in--. 
 
 Washington, />. ('., March 20, W0J h 
 
CONTENTS, 
 
 !',!■'. 
 
 Additions to our knowledge of life histories 
 
 Euphorbia rust ( I 'rovn/eex euphorbia? C. ant] P.) 
 
 Sunflower rusl i Puecinia helianihi Schw.) 
 
 Crown rusl of oats P i rhamni [Pers.] Weltst.)... . 
 Segregation of host plains 
 
 Black stem rust of Agropyron and Elymus 
 
 ( (range leaf rust of Agropyron and Klymus 
 
 Black stem rust of Agroslis nll><t vulgaris 
 
 Rusl of Chloris I Puecinia vhlorid'ix I Met. ) 
 
 Rusts i't' willow ami cotton " 1 i Melampsi >ra I 
 
 Winter resistance of the uredo 
 
 llredo of Kentucky hluegrass rust I Puecinia poarum Niels. 
 
 I redo of Pucciiiiti ntontanensis Ell 
 
 Emergency adaptations 
 
 Puecinia rej'anx Far! 
 
 Experiments with Lepto-uredinere 
 
 Rust of cocklebur i Puecinia ranthii Schw. i 
 
 Rust of velvet lea ' rospora l">. and ('. i 
 
 Perennial species 
 
 / tuberculatum E. and K 
 
 Rusl of Peueetlanum fn nieitlaceum 
 
 Description of plates 
 
 9 
 9 
 
 II 
 13 
 1 I 
 15 
 17 
 17 
 is 
 is 
 19 
 20 
 20 
 21 
 22 
 
 26 
 26 
 27 
 •J7 
 28 
 32 
 
I ILLUSTRATIONS 
 
 Page. 
 
 Plate I. A perennial rust Frontispiece. 
 
 II. Rusts of Euphorbia and grama grass. 32 
 
 8 
 
K !• 1 V. P. I'. 1 117. 
 
 INVESTIGATIONS OF RUSTS. 
 
 ADDITIONS TO OUR KNOWLEDGE OF LIFE HISTORIES. 
 
 In in;iii\ instances, without any experimental proof, it is inferred 
 thai there is a connection between the different forms of rust occur- 
 ring on the same hosl plant simply because of their constant associa- 
 tion with each other. Sometimes it is afterwards demonstrated that 
 these inferences are wrong, though they are probably correct in a 
 majority of cases. Studies of the following species were made with 
 the \ iew of obtaining a more accurate knowledge of their life history. 
 
 El phorbla Rust {Uromi/ces euphorhia ( '. and P.). 
 
 Until the experiments herein described were performed it hail not 
 
 been del istrated that there is am connection between the svcidial 
 
 and other stages of this species, although experience naturally leads 
 one to think that there i-. They are in very close association on the 
 same plant, the jecidium appearing first, quickly followed by the 
 uredospores. In the spring of L893 Mr. J. B. S. Norton, now pro- 
 fessor of botany at the Maryland Agricultural College, while engaged 
 in experiments in the germination of weed.- in the greenhouses of the 
 Agricultural Experiment Station at Manhattan. Kan-., called the 
 w liter'- attention to a very young rusted seedling of Euphorhia </< ntata. 
 In this instance, as is usually the case with the 3'oung plants of this 
 host, the pod- were first badly affected by secidia. This fact, taken 
 together with the common observation that the seed pods of this host 
 are usually affected by all stages of the rust, lei I at once to the thought 
 t hat it was a case of rusl propagation through the medium of the germi- 
 nating seed of the host, something not before demonstrated for any 
 other -peri,- in the entire group of Uredinese, so far a- the writer 
 know-, unless we except the single instance of the experiment- of 
 Doctor Eriksson with Puccini a ghimaruin. b The seed used by Mr. 
 
 a Vie latente et plasmatic) ue <le certaines Uredin£es. (' pi. Rend., 1897, pp. 
 
 177. 
 '< T. s. Ralph, in Victorian Naturalist, Vol. VII, p. 18, describes an instance of a 
 rust attacking the seed of s stating thai " with the microscope we are 
 
 able to trace the fine yellow sporular mallei- into the covering of the seed, and into 
 the seed itself;" but apparently it was not determined by further investigation 
 whether or nol the rusl was able to reproduce itself through the germinating 
 
 9 
 
10 INVESTIGATIONS OF BUSTS. 
 
 Norton was examined and the pods were found to be badly affected. 
 Moreover, he stated that the seeds were planted without shelling. But 
 the writer did not know then, as he does now. that this fact would 
 probably make little difference, since the naked seeds are commonly 
 affected, often showing actual peridia. 
 
 To test the theory of rust propagation above mentioned, experiments 
 were instituted on April 22 for growing plants from rusted seed under 
 a bell jar. The seed used bore all stages of the. rust. The experiments 
 were in live series: (1) Seeds shelled and disinfected by mercuric 
 chlorid; (2) seeds unshelled and disinfected; (3) seeds shelled, but not 
 disinfected; (1) seeds unshelled. not disinfected; (."») like series No. -f, 
 but rusted mainly with secidium. All were planted in pots in a 
 greenhouse and the pots were kept under bell jars. On May L the 
 plants began to come up. After about three months, when the plants 
 had grown to a height of 3 to 5 inches, no rust had appeared on series 
 1 and -J, and only one spot on one plant of series 3. The plains of 
 series 4 and 5 were much rusted, the secidium appearing first, fol- 
 lowed shortly by uredosori. 
 
 On April 25, 1893, it was attempted to germinate teleutospores of 
 rust from the seeds used in these experiments, in water-drop cultures, 
 which resulted in failure. On June 28, 1893, a similar culture of the 
 fresh uredospores failed to germinate in two days. 
 
 In 1895 rusted seeds of Euphorbia <A ntata, sent from Kansas, were 
 planted in the greenhouse of the Department of Agriculture, at Wash- 
 ington, I). C. From these three plants grew, which were kept under 
 a bell jar. Soon one of these plants rusted badly, first with the secid- 
 ium, then a slight amount of the uredospores, and later the teleuto- 
 spores. It should lie remarked here that Kuphorbia rust, so far as 
 reported, occurs only on K. maculata in the vicinity of Washington, 
 D. C.,and the writer has never vet been able to obtain rusted seeds in 
 that region. 
 
 On December 11, 1896, a third series of experiments was started at 
 Washington, D. C. On that date rusted seeds of Euphorbia </> ///i/f>/ 
 from Kingman and Manhattan. Kans., were planted and kept under a 
 bell jar as before. Eleven plants resulted by December 26. On March 
 8, 1897, spermogonia appeared in considerable amount on the young 
 leaves of one plant, with a tendency to form a sort of hexenbesen. 
 
 On March 2i» two more plants were rusted, one with spermogonia 
 only on the young leaves, and the other with iccidia on the fruit. 
 On April lo still another plant showed spermogonia, making four in 
 all, out of the eleven, that became rusted. (See PL II. tig. 1.) 
 
 As above stated, the proof that the rust actually penetrates the hulled 
 seed is readily obtained, not only from microscopical demonstration, 
 but also from the fact that the actual peridia may often be seen with 
 the unaided eye in the seed. These experiments, however, further 
 
-I NFLOWEE RUST. 1 1 
 
 demonstrate the ability of the nisi to propagate itself through the 
 medium of the germinating seed of the host, and also make it seem 
 probable thai this is even the sommon method of reproduction in the 
 case "l it- occurrence <>n Euphorbia dentata. 
 
 It will lir noted also thai the results of these experiments make it 
 almost certain thai the /Ecidium and LTromyces appearing upon the 
 plants are "in- and the same species, since in every case all stages 
 resulted from planting the rusted seeds, the secidium appearing first, 
 then tin' uredo, ami then the teleutospores. If anything was lacking, 
 however, the proof lias since been made complete by the experiments 
 of Dr. .1. ( '. Arthur, as reported in tin* Botanical Gazette," in which 
 the uredospores and teleutospores were obtained on Euphorbia nutans 
 from a sowing of secidiospores from other plant- of the same host on 
 June 20, L899. 
 
 A.s is well known, the Euphorbia rust is widelj distributed overthe 
 United States, occurring on numerous host species, but it is probably 
 mostabundant on E. dentata and E. preslii. It is a significant fact. 
 bearing upon the ontogeny of the species, that it i- also on these two 
 hosts, particularly on /•.'. dentata, that the aecidium is most common, 
 and that tin' rusl attack- the seed so severely. The seed pods arc also 
 affected considerably in the cases of A', lata and /:'. rnargi nata. 
 
 On June 12, L897, tecidiospores of this rust had germinated very 
 well in water drop culture after three days, and on June 'I'l. after a 
 two days' culture in water of both the tecidium and uredo from 
 Euphwbia marginata^ the latter germinated sparingly, but the former 
 not at all. In no instance could the teleutospores be germinated, 
 though germination was not attempted \w\ often. 
 
 The writer has collected all three stages of this nist on Euphorbia 
 
 [data, A', marginata, I:', dentata, /'.'. preslii, E. glyptosperma, and 
 
 '•.'. hettvophylla. On E. jpetaloidea and E. seipyllifolia only the uredo 
 
 and teleuto stages were found, and on /*.'. lata and what was probably 
 
 A', geyeri even the uredo was rarely seen. 
 
 Si m lower Rust {Puccinia helianthi Scuw. i. 
 
 Although Saccardo rightly regards this species of Schweinitz as 
 quite distinct, and includes with it the ^Ecidium often associated on the 
 9ame host, in many herbaria the authority of Winter and Burrill is 
 followedin making it a form of Puccinia ta?iaceti, while the ^Ecidlum 
 i- commonly referred to . K'nli n m compositarum, a convenient dump 
 ing ground for numerous uncertain forms. The writer has always 
 considered this disposition >>\ the species to he without any good 
 rca- \cn on a purely morphological basis, and now the experiments 
 
 Utliur. .I.C.. "Cultures of Uredinwv in 1899," Bot Gaz , Vol \\l\. No. I. 
 pp. 270-271, April, L900. 
 
12 INVESTIGATIONS OF RUSTS. 
 
 here recorded make it rather certain that Schweinitz and Saccardo are 
 correct. So far as this country is concerned, the writer is convinced 
 that P. tanaceti either belongs almost entirely to tanacetum or does 
 not exist at all. So far it has been utterly impossible, even in a green- 
 house, to make transfers of the uredo from one to another of the 
 numerous supposed hosts of that species, except among hosts of the 
 same genus." It is, at any rate, pretty certain that the forms occurring 
 on Vernonia, Helianthus, Actinella, and Aplopappus, which have been 
 referred to /'. tanaceti at various times, should he considered distinct. 
 
 The circumstances connected with the culture experiments with this 
 species were in themselves peculiar. Late in the autumn of 1897 at 
 Manhattan. Kans., it was desired to obtain fresh material of the uredo 
 for inoculating various hosts, but at that date very little else than the 
 teleuto stage could be found. Finally, on October '2U a small amount 
 was found on Helianthus petiolaris, mixed among a much larger quan- 
 tity of teleutospores, and from this material sowings were made on //. 
 petiolaris and //. annuus. On November 8 there resulted one rust spot 
 on the latter host and three on the former. The spots were of the 
 uredo stage, but the interesting feature accompanying this culture was 
 the appearance first of spermogonia in one of the spots. This fact 
 made it probable that a part of the infection resulted from the teleuto- 
 spores of the inoculating material, even at this unusual season for the 
 germination of these spores. On March 7, 1898, while stationed at 
 the University of Nebraska, inoculations of //. petiolaris were again 
 made with the teleutospores only from other plant-, of the same host, 
 from which numerous spermogonia appeared in eight days, followed 
 shortly by eecidia, which were fully developed by November 1. By 
 these results the connection of the different stages of the rust is pretty 
 well established. At the same time it is shown that the forms on 
 //. petiolaris and //. annuus are identical. In all cultures made of 
 this rust both the uredospores and teleutospores have been found to 
 germinate easily and produce infections readily. Reverse cultures 
 with secidiospores were not made. 
 
 These experiments were first reported at the L900 meeting of the 
 Society for Plant Morphology and Physiology, at Baltimore. Since 
 that time Drs. .1. C. Arthur'' and W. A. Kellennan' have made a 
 number of such experiment-, confirming these results, bul also seem- 
 ing to indicate a distinction of host forms on different species of sun- 
 
 "Dr. M. Voroninat first also obtained negative results in similar experiments in 
 Russia in attempting transfers of the rust on to other hosts. (See Bot. Zeitung, vol. 
 30, pp. (>w4 698, Sept. 27, L872.) Later he obtained infections of Puccinia tanaceti 
 from Tanacetum vulgare on sunflower, which, however, did not produce such vigorous 
 gro^ ih as ordinarily. (Bot. Zeitung, vol. '■'<■>, pp. 340,341, May II, ls7">. i 
 
 ^Botanical Gazette, vol. 35, p. 17, January, L903; Journal of Mycology, vol. lit, 
 pp. 12 l:;, January, L904. 
 
 c Journal of Mycology, vol. 9, pp. 230-2.".2, December, 1903. 
 
( i;m\\n ki - i OF VTS. 1 3 
 
 flower. Doctor Voronin, in bis experiments above mentioned, also 
 found thai rusl of cultivated sunflower would not infect Tlelianthm 
 tiil>, rosus. In l'.'oi Ernst Jacky " inoculated the following hosts with 
 teleutospores from Tlelianthm tinnitus: II. annum, II. citcumerifolim, 
 II. call '/ ',,/■/, I, us, II. tuber/mis, II. maximiliana, II. mitftijforus, II. 
 scaberi/n us, and //. rigidus, with resulting infections of the three first- 
 named species, but no infection of an\ of the others. 
 
 The evidence from all these experiments jusi quoted and those of 
 the writer shows at leasl that the rusts of Tlelianthm annum (includ- 
 ing cultivated varieties), //. petiolaris, and //. mollis are identical. 
 with the probability thai a distinct form exists <>n //. tuberosum. 
 
 Sunflower rusl has been collected by the writer on the following 
 species of rlelianthus, including all stages on nearly every species: 
 //. annum (both wild and cultivated), //. rig id as, II. petiolaris, II. 
 tuberosus, II. hirsutus, Il.niaxuniliana-, II. grosse-sewatus, II. orgyaltx, 
 II. mollis, and //. ciliaris. The secidium occurs rarely in compari 
 son with the occurrence of other stages, but is to be found on a num- 
 ber of hosts and occasionally in considerable abundance. This rarity 
 of it- occurrence, together with the occurrence of spermogonia so 
 often with the uredo, ma\ be accounted for by the fact that the uredo 
 is often produced by direct teleutosporic infection. 
 
 Crown Rust of Oats (Puccinia rliamni [Pers.] Wettst.). 
 
 In a mere note in a previous bulletin of this Department 4 it is stated 
 that certain infection- had just been made showing the connection of 
 the crown rust of oats on Phalaris caroliniana and Arrhenatheruni 
 elatius with the recidial form on Rhamnus lanceolata. No other dem- 
 onstration of such a connection of form- had been reported up to that 
 time. During the same season, however, Doctor Arthur obtained 
 infections with the (ecidium of Rhamnus lanceolata on out- at Lafayette, 
 lnd. The experiments of the writer are here given in detail. 
 
 On August 23, L897, the uredo stage of a rust, supposed to be / 
 cinia coronata, was found in great abundance on Phalaris Carolinian 
 at Stillwater, ( >kla. This host, with the rust, was transferred to a green- 
 house of the Agricultural College at Manhattan. Kan-., and inocula- 
 tions were made on oats, wheat, and orchard grass on August 30, L897, 
 resulting September 7 in a good infection of oats, a poor one of the 
 orchard grass, and no infection at all of wheat. Other inoculations 
 were made September 1 on wheat and rye, with no result. By October 
 8 the teleutospores had appeai'ed on the original plant- of Phalaris 
 
 I .iirall.. Bakt. Parasit. u. Infekt, 2 Vbt., Bd. 9, No. 21, pp 
 1902. 
 
 I ereal Rusts of the United States, Bui. So. I(>, [)iv. of Veg. Phys. and Path., 
 1 - Dept. of Agriculture, 1899. 
 ■ Bui, Lab, Nat. Hist. State Univ. Iowa, Vol. IV, p] i, December, L898, 
 
 lic- 
 et 
 
14 INVESTIGATIONS OF RUSTS. 
 
 at Stillwater and were of the crown rust type. After this date the 
 experiments were continued at the State University laboratories at 
 Lincoln, Nebr., all host plants then in use being transferred to that 
 place. On November L<> the crown rust was found, in the uredo stage, 
 on Arrhenatherum < hit ins on the State University farm, and a rusted 
 plant was transferred to the greenhouse. On December 11 inoculations 
 with the rust were made on oats and rye, resulting in a good infection 
 of the former in twelve days, but with no result on the latter. Fur- 
 ther inoculations of oats with the Phalaris rust on February IB, 1898, 
 resulted again in a good infection in 9 days. 
 
 No species of Rhamnus is native near Lincoln. Nebr., but Rhamnus 
 lanceolata is rather common at Weeping Water, about 20 miles east of 
 Lincoln, where it is often badly rusted with .ZEcidium. From that 
 place a large amount of the .Fcidiuin was obtained fresh on -June 1, 
 1898. A water-drop culture of the material, made the next day, gave 
 a profuse germination of the spores in twenty-two hours. Inocula- 
 tions with the a'cidiospores on oats and Phalaris caroli/niana were 
 made .June 1 and June 2, resulting in a successful infection of Phalaris 
 on June 14 and of oats on June 18. The oat inoculations were made 
 simply on detached portions of the plant preserved with their broken 
 ends in water in a damp chamber. As in all other instances, these 
 inoculations were made with the greatest of care to prevent accidental 
 infections. The whole series of experiments proves (1) the connection 
 of the secidial form of Rhamnus with the crown rust of oats, and (2) the 
 identity of the latter with the forms on Phalaris caroliniana and 
 Arrhenatherum elatius, besides making it probable that orchard grass 
 may also support this species. 
 
 SEGREGATION OF HOST PLANTS. 
 
 The most important economic results of the study of rusts are likely 
 to be derived from the investigation of the relationship of the forms on 
 our common grasses. Such work has already been carried on to some 
 extent by the writer and partially reported in the bulletin entitled 
 "Cereal Rusts of the United States." A more detailed account of 
 some of this work will be given here. Because bearing upon the same 
 question, it seems proper to mention also some experiments with the 
 rusts of Salix and Populus. Probably the greatest confusion exists 
 concerning the identity of the different forms on Agropyron and 
 Kl yinus, though there is much uncertainty also about those occurring 
 on Bromus and other genera. 
 
 The experiments here described were conducted at Stillwater, Okla., 
 Manhattan. Fans.. Lincoln, Nebr., and Washington, D. C, the host 
 plants being sometimes transferred from one place to another. Of all 
 these rusts the one receiving most attention was the black stem rust 
 of Agropyron and Flymus. 
 
ltl.ACK STEM RUST OF AGROPYRON \NI» ELYMUS. 
 
 L5 
 
 Bla('k Stem K'i si ok Agropyron wi> Elymus. 
 
 At least three and probably four ditferenl rust*! occur on the species 
 of these two grass genera, and are often so closely associated tha( 
 their accurate identification is extremely difficult. Of the herbarium 
 specimens of these rusts throughout the country, probably not one in 
 fifty is identified with any certaint}'. The writer's experiments with 
 these forms are -till incomplete, bul a few things at leasl have been 
 established. When these grasses are brought under cultivation the 
 changed conditions and proximity to other grasses and grains cause 
 them in become much more rusted than is ordinarily the case. In 
 the cultivated grass plats at the experiment stations in Oklahoma, 
 Kansas, and Nebraska the rusts were found in great abundance. It 
 was therefore easy to carry on many culture experiments. These 
 experiments with the uredospores of Mack stem rust were sufficiently 
 numerous to make it desirable to arrange them in the follow ing table: 
 
 Taui I I ultun experiments with black stem rust of Agropyron and Elymus. 
 
 Date. 
 
 
 Origin of inoculating 
 material. 
 
 
 Washington, D.C. Wheat. 
 
 Do do do. 
 
 Jan 22, 1897 do do . 
 
 I '•■ do do . 
 
 Do do 
 
 Do do 
 
 Sept. 13 L89 Stillwater, Okla ... 
 
 Do do 
 
 ... Manhattan, Kans . 
 Do do 
 
 Do do 
 
 Do do 
 
 Oct. 21, 1897 do 
 
 Do do 
 
 Do do 
 
 Do do 
 
 I". do 
 
 Do do 
 
 Do do 
 
 Do do 
 
 1,1897 ... Lincoln, Nebr 
 
 Jan.5, 1898 do 
 
 ....do 
 
 ... do 
 
 Agropyron U nt rum .. 
 
 mini. 
 
 do 
 
 do 
 
 Jan. 21, l s '.i-> do 
 
 Do 
 
 I i 11, 1898 
 
 Do. 
 Do 
 Do 
 Do 
 
 Di 
 
 Do. 
 
 .do. 
 .do. 
 
 .do. 
 .do. 
 .do. 
 .do. 
 
 .do. 
 .do. 
 
 .do. 
 .do. 
 .do . 
 
 Agropyron occ 
 Wheal (originally 
 
 do 
 
 .I.. 
 
 do 
 
 do 
 
 do 
 
 do 
 
 Agropyron occidi ntale 
 clci 
 
 do 
 
 do 
 
 .do 
 
 Elymus in mull nsU 
 folius. 
 
 do 
 
 Wheal (originally 
 
 I'.hllh 
 
 .do 
 
 I\l l/lll Il- 
 l/Ill III i ! 
 
 .....do 
 
 do 
 
 riant inoculated. 
 
 Elymus virgii ■ 
 
 Wheal 
 
 Elymus I'irginicus 
 
 Agropyron richard- 
 soni. 
 
 Wheat 
 
 Agropyron occidi ntale 
 
 Wheal 
 
 Agropyron tt m 
 
 Wheal 
 
 do 
 
 Hurley 
 
 Agropyron tcnerum . . 
 
 w heal 
 
 Barley 
 
 
 
 Rye 
 
 Wheal 
 
 Rye 
 
 Barley 
 
 Agropyron I* m rum . . 
 Af/ropi/ron occidi utali 
 Wheat 
 
 
 Barlev. 
 Wheal . 
 
 .do . 
 .do. 
 
 .do . 
 .do. 
 .do . 
 
 Barlev 
 
 Rye 
 
 
 
 Elymus cumuli n*is 
 
 glaucifolius. 
 Elymus 
 Elymus virgi n icu s 
 
 muticus. 
 Elymus inli rmedius. . 
 
 ■ hi li in mm . . 
 
 Result. 
 
 Success, 
 Do. 
 Do. 
 
 Do. 
 Failure. 
 Succi 
 
 1 ><.. 
 Failure. 
 Success. 
 
 Failure. <■ 
 Success; 
 
 Do. 
 (rf) 
 Kiii hi re. 
 
 Do 
 
 Do. 
 
 Do. 
 
 Do 
 Success. 
 
 Do.« 
 
 I >". 
 Do, 
 
 Do. 
 
 II Do./ 
 
 II Do 
 
 1 1 Failure. 
 
 ll Do. 
 
 II Mi 
 
 ll Failure. 
 
 II Do. 
 
 II Do. 
 
 II I >n. 
 
 II Do. 
 
 a Pustules differ in color from the original. 
 '■l pustule only. 
 
 i itions \ cry unfavorable, li"» 
 
 d Apparently l pustule fonm 
 
 • Rusi changes color and form of pustule. 
 
 ' RusI changes color. 
 
16 INVESTIGATIONS OF RUSTS. 
 
 Table I. — Culiun < vp< rirm nls iirith black stem rust <■/ . [gropyron and Elymus— ( lontinued. 
 
 Date. 
 
 Locality. 
 
 i >rigin of inoculating 
 
 material. 
 
 Plant inoculal ion. 
 
 Period 
 of incu- 
 bation 
 
 in daj - 
 
 Result. 
 
 Feb. 11, 1898.... 
 
 lie, 
 
 Lincoln, Nebr 
 
 .1.. 
 
 Elymus virgirt 
 do 
 
 K/ii mux virgin icus 
 
 lllllli, ll>'_ 
 
 Elymus canadensis 
 
 glaucifolius. 
 Agropyron U nerum. .. 
 Agropyron occidi n- 
 
 tali 
 Rye 
 
 13 
 13 
 
 13 
 
 13 
 
 13 
 
 13 
 13 
 
 7 
 
 11 
 'J 
 
 Sllcce-s. 
 
 Do 
 
 1 1,1 
 
 do 
 
 do... 
 
 1 10 
 
 Do 
 
 do 
 
 do 
 
 Do 
 
 Do 
 
 do 
 
 ...do 
 
 
 Ho 
 
 do 
 
 do 
 
 Do 
 
 Do 
 
 do 
 
 do 
 
 Wheat . . 
 
 Do 
 
 Feb. 21, 1898 
 
 do 
 
 Wheal (originally 
 Elymus canadi nsii 
 glaucifolius). 
 do 
 
 Elymus canadensis. . . 
 
 Hordt a in jubat 
 Wheat .. 
 
 
 
 
 Do 
 
 Feb. 28, 1898 
 
 do 
 
 Elymus cana 
 ijlaucifolius 
 
 Do b 
 
 
 
 
 
 a Pustules differ in color from the original. 
 
 ''Knst changes in appearance. 
 
 The results of these experiments, considered in connection with those 
 recorded in Bulletin No. 16, Division of Vegetable Physiology and 
 Pathology, U. S. Department of Agriculture, appear to establish two 
 things, viz, (1) that the forms of black stem rust on wheat, barley, 
 Ilordeum jubatum, Agropyron t, m rmn, A. richardso?ii, Elymus cana- 
 densis, and E. cancul< ns'ix glaucifolius are identical, with the proba- 
 bility that those on Elymus virginicus, /:'. virginicus muticus, and 
 Holcus lanatus should lie included; (2) that the black stem rust of 
 Agropyron occidentale b is physiologically distinct from any other.' 
 
 A very interesting phenomenon in these experiments was the change 
 in color and form of sorus of the rust produced by a transference to 
 another host. Jn some eases after a transfer the rust was scarcely recog- 
 nized. The change of color was sometimes from a bright yellow to a 
 deep brown or orange, or the reverse. The uredo of Agropyron /i/i<- 
 riim. for example, was often very yellow on the leaves, but changed to 
 brown when transferred to wheat. On the specie- of Elymus the rust 
 has a brown, waxy appearance, and the teleutospores long remain cov- 
 ered by the epidermis of the host. 
 
 "On January 5, L900, quite successful infections <>n wheal were made with the 
 uredospores id' black stem nisi of this host. 
 
 & Probably the most correct name of this host, which is known also as [gropyron 
 
 spicatum and A. glaucui (Sec Hitchcock, "Note on X mclature," Science, vol. 
 
 17, pp. 827-828, May 22, (03. ) 
 
 'The form mi this host was described as a distinct species, named Pttcciniaagrojryri, 
 by Ellisand Everhart, in Journal of Mycology, Vol. VII, p. 131, March Hi. 1892, a 
 lad nut noticed by the writer until alter must of these experiments were made. 
 This species includes iridium clematidis l>. C. according to Doctor Dietel, the proof 
 of relationship being the resultof culture experiments. (Oesterr. Bot. Zeitschr., 
 No. 8, 1892.) 
 
OK V.NG I 1.1 \l Ki ST OF AOKOl'} RON \M> 
 
 ,YMI 
 
 17 
 
 Oranoe Leaf Liusi oi Aoropyron \m» Elymus. 
 
 In the following table are summarized the results of inoculation* 
 with the uredoform of this rust. Thej were carried on simultaneous! y 
 with those of the Muck stem rust, and the material was taken chiefly 
 from the same individual host plants. 
 
 Table II. - Culture experiments uith on st of Ayropijron and i i • 
 
 
 Locality. 
 
 i irigin of inoculating 
 material. 
 
 Kyi- 
 
 I'lanl inoci 
 
 Period 
 liatioii 
 
 I;. -mi 
 
 1896. . . 
 
 Washingl !>.(' . . 
 
 do 
 
 1 
 live.... 
 
 111 
 
 13 
 
 18 
 
 18 
 18 
 12 
 12 
 
 26 
 
 9 
 
 21 
 21 
 18 
 18 
 
 1 1 
 1 1 
 11 
 
 1 1 
 
 
 |>o 
 
 do 
 
 do 
 
 do 
 
 
 Jan. 7, IS97 
 
 Llo 
 
 do 
 
 do 
 
 HI il in ut 
 
 
 Fl -Ii. 1, \K>~.. . 
 
 ..do. 
 
 do 
 
 Rve 
 
 
 
 ...do 
 
 ...(In 
 
 
 1 
 
 ..:tlo . 
 
 Wheal 
 
 Agropyi 
 
 Wheal 
 
 Rye 
 
 1 
 / 
 Rye 
 
 
 Do 
 
 do 
 
 do 
 
 
 
 
 1897.... 
 
 Do 
 
 Ho 
 
 do 
 
 iln 
 
 do 
 
 do 
 
 do 
 
 (In 
 
 Manhattan, Kuns 
 
 do 
 
 do 
 
 Rye 
 
 do 
 
 do 
 
 Do 
 Do. 
 
 
 ....do 
 
 
 1897 
 
 ....do 
 
 Agropyi on 
 Rye 
 
 
 
 do 
 
 do 
 
 
 
 
 s 
 
 
 
 Do 
 
 do 
 
 
 
 Do. 
 
 
 ....do 
 
 do 
 
 Agropyron /• 
 
 Do. 
 
 
 
 do 
 
 do 
 
 do 
 
 
 
 
 Jan. ■">, 1898 . . . 
 
 
 
 do 
 
 Do. 
 
 Do.. 
 
 ....do 
 
 ...do 
 
 Wheat 
 
 Failure 
 
 M;ir. 1 
 
 do 
 
 niciis 
 
 / 
 
 Wheat ' 
 
 Do. 
 
 Do.. 
 
 do 
 
 
 Do. 
 
 Mar. 1. 
 
 ..do . 
 
 
 
 do 
 
 
 
 
 do 
 
 
 Elymu* eanadt nsis . .. 
 
 Failure 
 
 Hn..._ 
 
 do 
 
 do 
 
 do 
 
 Do 
 
 Do <1o 
 
 Do 
 
 
 
 
 The chief conclusion to lie derived from the results of these cultures 
 is that the orange leaf rust is very sharply limited in it- hosl adap- 
 tation and differs widely in this respect from the black stem rust. 
 Similar results are given in Bulletin No. 1*'' of the Division of Vege- 
 table Physiolog3 and Pathology, I'. S. Department of Agriculture, 
 for cultures of the form- on wheal and rye. In fact, it is quite proba- 
 ble thai almost every distinct host species bears a distinct form of the 
 rust. One of these forms on Elytnvs virginicus L. has recently been 
 found 1>\ Doctor Arthur to be connected with the .Kcidimii on Impa- 
 tiens aureu Muhl. and is now to be known as Puccinla imjwtivntU 
 (Schw.) Arth. ' 
 
 Black Stem Ki - i of Vorostis vera vulgaris. 
 
 Culture experiments with the uredoform of this rusl and observa- 
 tions in the lie Id indicate that it is distinct and doe- not occur on other 
 
 tanical Gazette, vol. 35, pp. I s 19, January, 1903. 
 l'77s: No. 63—04 2 
 
INVESTIGATIONS OF RUSTS. 
 
 hosts." The results of the culture experiments are given in the follow- 
 ing table: 
 
 Table III. — Culture experiments with black stem rust of Agrostis alba vulgaris. 
 
 Date. 
 
 Locality. 
 
 Origin of inoculating 
 
 material. 
 
 riant inoculated. 
 
 Pel iod 
 ■ it incu- 
 bation 
 
 in days. 
 
 Result. 
 
 Dec. 23, 1897... 
 
 Do 
 
 Lincoln. Nebr 
 
 do 
 
 Agrostisalba vulgaris. 
 do 
 
 Ag rostis alba vulgaris. 
 
 Wheal '. 
 
 Oats 
 
 s 
 
 8 
 s 
 12 
 12 
 
 11 
 
 Success. 
 
 Do... 
 
 ....do •. 
 
 do 
 
 I'd 
 
 Jan. 24, 1898... 
 
 ...do. 
 
 ...do . 
 
 Wheat . 
 
 Do 
 
 Do 
 
 ....do 
 
 ...do.... 
 
 Oats 
 
 Do 
 
 .Feb. 11, 1898... 
 
 .do. 
 
 Elymus canacU nsis 
 glaueifolius. 
 
 Ag ostii alba vulgaris. 
 
 Do. 
 
 
 
 
 The rust is evidently of the black stem rust group {Puccinia graminis 
 of authors), but contains quite a number of abnormal teleutospores, 
 including mesospores. Many measurements of these spores average 
 27-5i by 16-23yu, mostly 40^6 by 16-18/*. 
 
 Rust of Cheoris {Puccinia chloridis Diet.). 
 
 The uredoform of this rust is sometimes very abundant on Chloris 
 verticillata in the Great Plains region, occurring in late summer and 
 autumn. The sori are deep brown in color. The uredospores germi- 
 nate very freely and easily. In a number of experiments made in 
 1898 it was found that the uredo on C. verticillata and ( '. elegans 
 would readily transfer from either host to the other, but not to other 
 grasses, in several cases which were attempted. In a wat«h-glass cul- 
 ture, made March L8, L898, of uredospores from C. elegans, produced 
 from artificial infection in a greenhouse, not only these spores germi- 
 nated freely, but a number of newly formed teleutospores al the same 
 time, an occurrence unusual except in the Lepto-uredinese. Among 
 thousands of cultures made by the writer only one other instance of 
 this kind has occurred. In the summer of L895 at the Biological Lab- 
 oratory at Cold Spring Harbor. Long Island, both teleutospores and 
 uredospores taken from the same sorus id' a rust on Luzula campestris 
 gave good germinations. 6 
 
 Rusts of Willow and Cottonwood (Melampsora). 
 
 Both the uredospores and teleutospores of the rusts of willow and 
 cottonwood germinate readily, the germ tubes of the latter containing 
 always brilliant endochrome. Healthy leaves of either cottonwood or 
 willow placed in a damp chamber have often been infected by the 
 
 a Arthur describes culture experiments made by his assistant, William Stuart, in 
 .Inly, L898, in which wheat plants were infected with uredospores from this host, 
 hut the spores of the infection sori were larger than these of the original material. 
 (Bui. Lab. Nat. Hist, state Univ. Iowa, vol. I. No. 1, pp. 396 397, 1898.) 
 liic species was, without much doubt. Puccinia obscura Schroet. 
 
WINTER RESISTANCE OF THE UREDO. L9 
 
 wrih'i in nine to twelve days. The incubation period is tnuch short- 
 ened by using germinating spores in the inoculations. In the month 
 of October, at Manhattan, Kans., an infection was produced in tin- 
 way in three da^ s. 
 
 It was attempted by numerous inoculations with the uredoform, 
 chieih at Washington, I>. ('.. to transfer the rust from willow to cot- 
 tonwood and the reverse, bul always without success. An interesting 
 feature of thesa experiments was the discovery of the fad that the 
 cottonwood mosl common in Washington, known as South Carolina 
 poplar, could not be infected by the uredoform from the common 
 Western cottonwood, though these two poplars are classed h\ some as 
 being the same species. Moreover, the rust does not occur in nature 
 on the South Carolina poplar, bul is very abundant on the Western 
 cottonwood, and even occurs in Washington on the tew individual 
 trees of that type growing in the city. 
 
 WINTER RESISTANCE OF THE UREDO. 
 
 In another bulletin" the writer has given in detail the observations 
 ami culture experiments proving the successful wintering of the uredo 
 in the orange leaf rust of both wheat and rye. In this connection it 
 i- eu-\ t.i 3ee a number of closely correlated facts, which may mutually 
 explain each other: (1) As shown under the preceding topic, the uredo 
 of black stem rust may infect a number of different hosts, ami there- 
 fore ha> a manifoldly greater chance of propagation with the same 
 mun her of uredospores than if there were hut one possible host; (2) as 
 also shown, the uredo of orange leaf rust is restricted in every case to 
 hut one host, or at mosl to hut one genus, and a much greater produc- 
 tion of uredospores is therefore necessary for the life of the species 
 in this stage; (3) as a corresponding matter of fact it is well known 
 that the uredo of the latter rust exists usually in very much larger 
 quantity than that of the former; i 1 1 on the other hand, the teleuto 
 sporic stage is the prevailing form of the stem rust, which fact makes 
 this rust usually the more damaging of the two. a- the teleutospores 
 infest the stem chiefly, thus more directly interfering in plant nutri 
 tion; (5) the stem rusl is proved to he connected with the barberry 
 rust, thus giving it an additional chance for increased propagation, 
 ami this through tic medium of the teleuto stage instead of the uredo; 
 (6) finally, the uredo being the prevailing form of the leaf rust, and 
 Dosecidial form being known in this count ry,'' it would seem necessaiy 
 that this stage of that rusl should be very hardy in order to endure 
 extremes of cold and drought and preserve the life of the species. 
 Previous investigations of the writer and others have amplj proved 
 that tin- is the case. In t he meantime it is found that in other species 
 
 "Cenal Rusts -i the United State-. Bul. 16, Div. Veg. Phya. and Path., I' 
 Dept. of Agriculture, pp. 21 -l'::. ami II, !■">. 
 
 cept in the case of the form on / ijmua virgin i ready mentioned, 
 
20 
 
 INVESTIGATIONS OF RUSTS. 
 
 there exists a similar hardiness of the uredo, of which cases the fol- 
 lowing will be discussed here: 
 
 Uredo of Kentucky Bluegrass Rust (Puccinia poarum Niels.). 
 
 The writer has known for some time that the uredo stage of the blue- 
 grass rust is able to pass the winter alive and in germinating condition 
 during any season as far north as Lincoln, Nebr., but additional evi- 
 dence has been obtained from time to time. At the same time it is sig- 
 nificant that there is no record that the teleutospores have ever been 
 found, except in one instance, at the above-named place. In fact, lew. 
 if any, uredot'orms so hardy as this one exist in this country. On 
 February 1, 1893, this uredo was still alive in the vicinity of .Man- 
 hat tan. Kans. Every month of the year it exists alive and growing in 
 great abundance everywhere about Washington, D. C. On March 2, 
 1898, it was found fresh on green leaves of the host at Lincoln. Nebr. 
 On the same spot of ground it was still growing and spreading rapidly 
 on May 8 of the same year. Host plants were transplanted that day 
 into a greenhouse, where the rust continued to increase rapidly. As 
 would now be supposed, the rust is sharply limited to its one host. 
 Kentucky bluegrass. The results of the following cultures may be 
 given in evidence. 
 
 Table IN" . — Cullun experiments with the uredo of Kentucky bluegrass. 
 
 Date. 
 
 Locality. 
 
 Origin of inoculat- 
 ing material. 
 
 Plant inoculated. 
 
 Period 
 of incu- 
 bation 
 in days. 
 
 Result. 
 
 
 Manhattan, Kans . 
 do 
 
 Poa p att nsis 
 
 w heat 
 
 18 
 
 is 
 16 
 
 11 
 
 11 
 13 
 
 13 
 
 is 
 
 10 
 
 
 Ho 
 
 Oats 
 
 Do 
 
 Dec. 21, L89i 
 Jan. 22 1897 
 
 Washington, D.C.. 
 do 
 
 Rye {Uredo rubigo- 
 V/hed ( ' redo jra- 
 
 minis). 
 .Id 
 
 .. do. 
 
 Do 
 Do 
 
 Do... 
 
 
 noralis 
 
 Poa pratensls 
 
 Do. 
 
 1 897 . . . 
 
 .. do 
 
 Rye ( ( Vi do rubigo- 
 do 
 
 Do 
 
 Do . . . 
 
 do 
 
 Do. 
 
 Feb. 13, 1897.. . 
 
 ...do 
 
 Wheal < 1 ' 
 
 vera). 
 
 itensis 
 
 ... .do 
 
 Do. 
 
 Feb 15, 1 B97 
 
 .do. . 
 
 
 
 
 
 
 
 Uredo of Puccinia montanensis Ell. 
 
 This is, in some respects, one of the most interesting of grass rusts. 
 It is one of the "covered rusts," and is, indeed, so far covered that it 
 is often entirely overlooked by collectors. The uredosori are very 
 Uniform in size and are exceedingly small, it being necessary often to 
 examine them, or even find them, with a hand lens. They are ellip- 
 tical in shape and placed end to end in long, narrow, yellow striae 
 between the veins of the leaf. The teleuto stage is so far hidden as 
 to be detected only by a faintly darker color beneath the leaf epi- 
 dermis. The rust is the most nearly like /'. glvmarum Eriks. and 
 
EMERGENCY ADAPTATIONS. lM 
 
 Ilciin. ye\ found in this country. The known hosts are Elymus cana- 
 densis &nd /:. virginicas, but it seeuis to occur on other hosts. Whether 
 the forms on different hosts can be transferred from one to another 
 is not \ et fully determined: 
 
 The important fact now known, however, is thai the nredoform is 
 able tt> preserve the species over the winter without the intervention 
 of other stages, though it is possible that extensive propagation is 
 aided by other stages. October 28, 1897, fresh uredosori were observed 
 on Elymus canadensis at Manhattan, Kans. , and again in the same 
 locality on November 2. But as early in the spring as May 26, at 
 Lincoln Nebr., when there was yet but a small beginning of vegetation, 
 the uredo had burst the epidermis of the host in grass plats at the 
 University farm. Previous to this the living uredo had been observed 
 in the--e plats practically even month of the winter. 
 
 [n other instances the uredospores of certain species are so very 
 abundant and the teleutospores so rare that there seems a probability 
 that such species are carried over from summer to summer largely 
 through the uredo stage alone, though there is no absolute proof of 
 such a cour>e. Two instances are particularly interesting those of 
 the uredos of Puccinia cryptandri Ell. and Barth., and Puccini a on 
 Panicuni autumnale. The uredospores of these species begin to be 
 conspicuously abundant about midsummer, but continue in consider- 
 able abundance until very late in autumn. The uredo of Panicuni 
 autumnal i was found in germinating condition in Kansas up to Novem- 
 ber 3 in L897. A water-drop culture of uredospores of this species 
 gave excellent germination in ten hours August 21, 1897, at Perkins, 
 Okla. The uredospores of Pucciniacryptandri were found in extreme 
 abundance in Oklahoma until October 11, 1897, but in all cases with- 
 out any accompanying teleutospores. Often the uredosori had a fresh 
 appearance on portions of leaves that were quite dead. 
 
 EMERGENCY ADAPTATIONS. 
 
 In connection with some culture experiments conducted at Lincoln, 
 Nebr., in the botanical laboratory of the State University, in February, 
 l v '.'^. a water-drop culture was made (February 3) of uredospores of 
 the above-mentioned Puccinia cryptandvi which had been collected on 
 October 8, 1897, at Perkins. Okla.. and kept to date as herbarium 
 specimens. A fair germination resulted in twentj four hours. Spores 
 from the same collection were used on February 16 to inoculate seed 
 lings of Y"'" 1 '""' " s airoides, b with the result of the appearance of two 
 rust spots bj March 16. These spots ma\ really have appeared much 
 earlier and been overlooked, as they were very small and the host 
 
 Pi rhaps a new species, n Jiiilt further study. 
 
 ^Apparently this same Bpecies of rust had already been collected <<t\ Sporoliolus 
 in the same locality where the collection fr S. • ry/ilandri was made. 
 
22 INVESTIGATIONS OF RUSTS. 
 
 itself is well known to have extremely narrow leaves. Moreover, the 
 8 pores were not germinated when applied, and, bring from dried speci- 
 mens, the incubation period would naturally be long. Seedlings of 
 /S. cryptandri were not at the time available. On March 16 a second 
 water-drop culture was made from this dried material, resulting in the 
 germination of a few spores. 
 
 Teleutospores from herbarium specimens have often been germi- 
 nated, but the writer knows of no other instance of the germination 
 of dried uredospores, such spores being able also to infect a different 
 host. These observations and experiments indicate that we have 
 here a second step in the perfection of the uredo stage as a means of 
 propagating the species. The tirst step, the attainment of sufficien 
 hardiness to continue alive in the green plant over winter, has just 
 been discussed. Even in this case the uredo, although quite active. 
 at least displaces the resting spore, and in a measure performs its pari . 
 But as the perennial host becomes more like an annual and the plant 
 dies nearly or quite to the ground, as in this particular case of the 
 Sporobolus (which is quite different in this respect from the evergreen 
 Poa pratensis, for example), necessarily, in the absence of teleuto- 
 spores, the uredospore must be able to infect after a dormant period. 
 The uredospore therefore becomes now practically a resting spore, 
 but retains the appearance and manner of germination of the summer 
 spore. Such a modification in form or function of any stage of a 
 species to correspond with an unusual change of condition of climate 
 or of the host may be considered as an emergency adaptation. 
 
 It is easily understood how the change of conditions may be so 
 severe as to necessitate still further modification of structure as well 
 as function, simply as a means of protection. Such a development 
 seems to have been actually reached in the species next discussed, 
 which has resulted in the production of a distinct spore form, special- 
 ized from the uredo. leaving still, however, a true uredo stage for 
 summer propagation. 
 
 PUCOINIA VEXANS FAKL. 
 
 There are probably no other species in all the Uredinese more inter- 
 esting than this one, and certainly none that has been more perplex- 
 ing. In this species there are three distinct spore f on us aside from any 
 secidium or spermogonium that may possibly exist true uredo and 
 teleuto stages, and a peculiar one-celled form different from either of 
 these. (PI. II, tigs. 2 !».) The species was at fust made all the more 
 puzzling by the rarity of the true uredo stage, which was not known 
 to exist, or at least not reported, until L890, when Dr. II. J. Webber, 
 in the Catalogue of the Flora of Nebraska, reported its occurrence in 
 that Stale. In certain seasons ami localities I he teleuto stage also is 
 almost or entirely lacking 1 . 
 
PTTCCIN1 \ VEX \N- FARL. 23 
 
 The species was first described h\ Peck as a Uromyces(?Z Irmndegei 
 l'k.i .in the basis of material collected by Mr. T. >. Brandege, in 
 which specimens contained only the third spore Porm. Because of the 
 discovery afterwards of two-celled spores associated with this third 
 spore form, even sometimes in the same sorus, Doctor Farlow described 
 it as a Puccinia </'. vexans Farl.) in the Proceedings of the American 
 Academy of Arts and Sciences, Vol. XVIII, pp. S2 S3. At that time 
 the true uredo stage bad not been discovered. 
 
 This third spore form is far more prevalent than either of the others 
 as a rule, bul is sometimes entirelj absent, leaving only the teleuto 
 stage. It is distinct from either of the other forms in structure and 
 appearance, and yet resembles both in some respects. It is larger than 
 either of them, i- strongly papillate, and ha- a much thicker cell wall. 
 but on the other hand possesses the color and persistence of pedicels 
 of teleutospores ami appears to have pores like the uredospores. (PI. 
 II. fig. 5. ) Doctor Farlow, in his description, says: 
 
 \ species in which some of the sori contain only two-celled spores must certainly 
 ! i.. be a Puccinia, and the perplexing question arises, are the one-celled spores 
 a unilocular form of teleutospores similar to what is known in /'. cesatii Schr., or are 
 ilny the uredospores of this species? 1 have not heen able to find any other spores 
 which represent the uredo of the species; ami never having seen the unicellular 
 spores in germination, there i>, -•> far as we yet know, no reason why they may not 
 be the uredospores. On the other hand, their general appearam e ami the density 
 of the cell wall would lead one to suppose that they were of a teleutosporic nature. 
 Further conjecture is unnecessary, because, as the species is not at all rare in some 
 localities, botanists who can examine the fungus on the spot ought to he able t<> 
 ascertain whether the one-celled I"" lies produce promycelia or not, or else to discover 
 the line uredo of the species. 
 
 A full description of all three forms is given by Arthur ami Holway 
 in Descriptions of American Uredineaa accompanying Fasiclo [V of 
 I redinese Exsiccatae el [cones. 
 
 After numerous unsuccessful trials during several years, the writer 
 was finally able to germinate the third spore form. and. as suggested 
 by Doctor Farlow, has in this way heen able to determine its nature. 
 In manner of germination it is exactly like the uredospore, the long 
 simple germ tubes being produced through equatorial pores (PI. II, 
 figs 7 and 8), but is like the teleutospore in germinating only after a 
 dormant period and exposure to extremes of weather. The uredo ami 
 teleuto forms being already presenl and morphologically differenl 
 from this form, ii musl he considered distinct. Because of the dual 
 nature of this spore form, the writer has already proposed for it tin' 
 name amj)/tisport in a paper read before the Baltimore meeting of the 
 
 Societ}' for Plant Morphology and Physiology in 1- , onl\ an ihstrad 
 
 of which was published. The term has since heen adopted by Arthur 
 
 I'-' I ..i/., -J: r_>7. 
 
 Bul. Lab. Nat. Hist. Man- Univ. Iowa, Vol. Y, pp. :;■_".< 330. 
 
 -nee. Vol. XIII, p. 250. 
 
24 INVESTIGATIONS OF RUSTS. 
 
 and Holway," and a second instance of the occurrence of this form is 
 described by them for Puccinia tripsaci Diet, and Holw. The entire 
 series of observations and experiments with this species made by the 
 
 write]- will now be described. 
 
 The first cultures of amphispores were made January L5, L894, at 
 Manhattan, Kans. Both a water culture and one of a sterilized decoc- 
 tion of manure were employed, with no result, the chief cause of fail- 
 ure being probably that the experiment was too early in the season. 
 Afterwards numerous other trials were made with no better success. 
 In the meantime true uredospores were found on September 25, L896, 
 at Manhattan. Kan-. 
 
 Finally a successful culture of the amphispores was made on March 
 8, 1897, at Washington, D. C. The germination was excellent. An 
 abundance of rather lone- germ tubes, not promycelia, was produced 
 in forty-two hours, but only one to each spore. These germ tubes, 
 unlike those of most uredospores. are quite colorless and clear. A few 
 teleutospores were present, none of which germinated. The culture 
 was an ordinary water drop, but was made in a new form of culture 
 cell, constructed to special order and similar to the Van Tieghem 
 cell, except that the elass ring is quite thin and drawn out into an 
 open tube on each of two opposite sides, with the opening plugged 
 with cotton wool, thus admitting sterilized air. This construction may 
 or may not have increased the chances for germination. The extreme 
 weather conditions at the time, to which the specimen- were first 
 exposed, probably contributed most to the success of the culture. 
 They were fastened to the roof of a near-by shed, and after several 
 days of warm sunshine were thoroughly soaked with rain, which was 
 followed by snow and then a severe freeze, soon after which the cul- 
 ture was made. It is an interesting feature of the experiment that 
 the specimens were received from Dr. David Griffiths, then at Aber- 
 deen, S. Dak., and had been collected in September, 1896, and kepi in 
 the herbarium until sent to Washington. It was unfortunate that 
 seedlings of the host were not available for making inoculations with 
 these perfectly viable spores. Such an experiment is yet to be made. 
 
 At .Manhattan. Kans.. in 1897, the uredo was present in considerable 
 abundance from June until late in October in grass plats on the 
 Experiment Station farm. On duly S inoculations were made with 
 the uredospores of this species and with iridium cephalanthi and 
 . /■'. xanthoxyli on seedlings of Bouteloua racemosa without result. 
 Further inoculations with uredospores on October 4 were successful, 
 rust spots appearing in twelve days (Fl. II. lie. '■'). followed in nine 
 more davs with one sorus of amphispores. The uredosori are yel- 
 lowish-brown and rather inconspicuous. On December 31 uredo- 
 spores could not be found in the grass plats at Manhattan. 
 
 "Bui. Lab. Nat. Hist., State Univ. towa, Vol. V, p. I7.'>. 
 
RXPERIMEN rS WITH I.I PTO-1 111- KIM 1 . 
 
 At Lincoln, Nebr., a water-drop culture was made of Puccinia 
 vexa/is'on March L5, LS98, resulting in a few germinations of the teleu- 
 tospores in three days. Long pronrycelia were produced, bul no 
 sporidiola. Nunc of the numerous amphispores present germinated. 
 
 On September 29, L899, all three spore forms were again found in 
 the grass plats at Manhattan. Living hosl plants were transferred i<> 
 Washington, 1>. C, and seedlings were started for further experi- 
 ments, when other duties intervened and the work could not be 
 continued. 
 
 Certain facts concerning the relative abundance of the amphispores 
 and teleutospores in differenl seasons and localities seem to harmonize 
 quite well with the idea already expressed as to the function of the 
 former. If it is the work of the amphispore to carry the species 
 through unusually severe cold or drought, then this spore form should 
 lie relatively more abundant in dr\ periods and relatively more com- 
 mon to the westward and northward in the Great Plain-. These con 
 ditions are jusl whal exist. The amphispore prevails almost entirely 
 in the Dakotas and in western Kansas, western Nebraska, and eastern 
 Colorado, and appears to have been more common in eastern Kansas 
 during a dry period of several years than during a wet period. At 
 the same time westward toward the mountains there i- less chance for 
 an .Kcidiuni to connect with the teleuto -lane. 
 
 EXPERIMENTS WITH LEPTO-UREDINEJE. 
 
 It is generally supposed that teleutospores which ah x followed by 
 an tecidium germinate only after a considerable period of rest, usually 
 in early spring. As already mentioned under the discussion of sun- 
 flower rust, the writer germinated teleuto- pore- of this species readily 
 in the autumn, and afterwards at differenl times during the winter. 
 This readiness of germination, apparently at almost au\ dale, is an 
 indication in itself of an alliance to the lepto species. But, more than 
 this, the autumn inoculation- with material in which no uredospores 
 could positively be detected nevertheless were, in some cases at least, 
 followed first by spermogonia and then bj the uredo! < )f course occa- 
 sional uredospores that may have been overlooked could have produced 
 those few spots in which the presence of spermogonia was not certain. 
 Here, then, i- further evidence of the lepto tendency of the species. 
 In addition, it i- well known that the a?cidium i- rare and appeal's to 
 have no fixed time of occurrence. Now. onl\ the omission of the 
 uredo is needed to make the rust a real lepto species. A- it i-. it- 
 position ;- more nearly that of a Hemi puccinia than of an autcecious 
 species. Experiments of this kind, united with critical field observa- 
 tions, thus throw much light upon classification a- to group position, 
 a- well a- enabling us to connect stages. 
 
 < )u the other hand, certain lepto species will he found to closely 
 
26 INVESTIGATIONS OF RUSTS. 
 
 approach other groups, and, indeed, after further experiment, may 
 have to be placed in some other group. The following species have 
 given interesting results in culture experiments. 
 
 Rust of Cocklebur (Puccinia xanthii Schw.). 
 
 Observations and culture experiments of the writer show that the 
 rusl of cocklebur is probably limited to one host and is distinct from 
 the species on Ambrosia, and also justify the suspicion that it lies very 
 near the border of the Lepto-uredinese, and may belong to another 
 group. 
 
 On March 1, 1897, the first water-drop culture made gave an excel- 
 lent germination in forty-eight hours. Long promycelia were pro- 
 duced, but no sporidiola. On February 13, L897, at Washington. 
 D. C, inoculations were made on seedlings of cocklebur and Ambrosia 
 trifida, resulting in an infection of the former in eighteen days, but 
 not of the latter. On March 12 a second experiment resulted in a 
 large number of infections of cocklebur seedlings in fourteen days. 
 In all these cases spermogonia preceded the teleutospores in the 
 infected spots. On October 8 of the samej^ear an aecidium was found 
 on cocklebur in considerable abundance, associated with the teleuto- 
 sori. at Perkins, Okla. An inoculation on cocklebur seedlings, made 
 at Lincoln, Nebr., on February l(i. L898, resulted in the production 
 of spermogonia in ten days. The inoculating material had been col 
 lected in October, L897. An aecidium on cocklebur was again found 
 in abundance at Las Cruces, N. Mex., on duly II. L899. Attempts 
 should be made to infect the cocklebur with this secidium. Doctor 
 Farlow says an secidium on Xanthium in Massachusetts is frequently 
 followed by Puccinia xanthii. 0. 
 
 The ease with which artificial infections are made with this rusl is 
 at first sui-prising. So long as there i-< warmth and moisture, germina- 
 tion occius under almost any condition and at any time. 
 
 Rust of Velvet Leaf (Puccinia heterospora B. and ('.). 
 
 In the last-mentioned experiments the inoculating material was 
 
 taken each time from dead leaves. The same was true in one experi- 
 ment with the rust of velvet leaf. November 1-1. L896, at Manhattan, 
 Kans.. in which seedlings of the host were infected in twelve days. 
 For all these experiments the average time of incubation was about 
 twelve days. In December, L896, the infected plants of the last 
 experiment were transferred from .Manhattan to Washington. D. C, 
 and material From these was used to inoculate new seedlings, which 
 resulted in an infection in nine days. It appears, therefore, that the 
 
 "Proc. Amer. Acad. Arts and Sci., Vol. Will, p. 75. 
 
PERENNJ \l. SPECIES. '11 
 
 incubation period is shorter if inoculating material is taken from liv 
 ing plants, and during the summer il is probably about the same as 
 that of infections from uredospores. 
 
 Numerous experiments were also made with other lepto specie-. 
 including Pucchria grindelix, l'k.. /'. variolans, Hark.. /'. lygodesmix, 
 Y.. and E., and /'. sherardlaitti, K6rn, with results similar to those 
 above mentioned. The writer 1 in -. already called attention to ihe 
 phenomenon of the formation of ratenulate sporidiola in two of these 
 species, /'. gi'liidelin and /'. variolanx." 
 
 PERENNIAL SPECIES. 
 
 The chance for the continued existence of a rusl through winter 
 resistance of the uredo without the intervention of another stage has 
 been discussed. Though such a condition can only exist on a peren- 
 nial host, or at least one thai lives over winter, it must not be sup- 
 posed that the fungus itself is necessarily or even usually perennial. 
 As fa-t as the leaves of the host die the spores simply drop on to the 
 next lower and younger leave- and produce reinfection, the mycelium 
 not extending through the base of the infected leaf into the next 
 leaves. If. however, the mycelium is found within the rootstock and 
 after a dormant period during midwinter follows the new -hoots 
 upward in early spring and again produces sori at the surface of the 
 plant, the rust is a true perennial. This condition appeal- to exist in 
 the follow ing species. 
 
 .Ki Hill VI ll BERCULATUM E. AM) K. 
 
 It i- now u-uallv supposed that all aeidial forms will likelv lie found 
 to lie connected with other stages, though there aie probably more of 
 these form- whose connection- are at present undetermined than there 
 are of Lepto-uredinere. If any .Kcidimn is more likely than another 
 to lie an independent species, certainlv the probabilities are largely in 
 favor of this species, which occurs on Callirrhot invohtcrat<t, b for there 
 i- no need of another stage to perpetuate it. though another host 
 might u'iv e il a w ider dist ribution. 
 
 The striking orange yellow color, large and otherwise conspicuous 
 sori, and it- complete attack of everj portion of the host make this an 
 unusually unique and attractive species (PI. I. frontispiece). A note con- 
 cerning the hardiness of this species was published l>v the writer sev- 
 eral years ago. The word- are here quoted: "jEcidivm tuhercidatum 
 
 " Bot, Gaz., Vol. Will. pp. 155 156 
 
 '* Tin >iil_'Ii ii. ii previously reported, this rust we founil also on ('aUirrhot <th 
 :\\ Salina, Kans., in May, 1893. 
 ■ Bot. Gaz., Vol. Will. p. I.',::. 
 
28 INVESTIGATIONS Oh { BUSTS. 
 
 E. and K.is still producing secidiospores on ( 'aUirrhot invohicrata out- 
 doors here tit Manhattan al the time of this writing (October L5, L893), 
 and Mr. E. Bartholomew, of Rooks County, Kans. , tells rne that be lias 
 seen in December aecidiospores on specimens of this host growing close 
 by a large snowdrift. In the spring aecidiospores of this species begin 
 forming about the first day of April." On December 20, 1893, after 
 the above was transmitted for publication, the rust was found still alive 
 although it had boon under 4 inches of snow. In a water-drop cul- 
 ture of some of the material four spores germinated in twenty-four 
 hours. Since that time, at later dates in the winter the living rust has 
 been found, but close within the rootstock, with a faint color still, 
 but producing no spores. The peculiar manner of growth of the rust, 
 permeating the entire host and producing scattering sori all along 
 the stems to their liases, as well as on the leaves, and the difficulty of 
 germinating the spores harmonize also with the idea of a propagation 
 by perennial mycelium. Besides the above instance other cultures of 
 the spores were made as follows: At Manhattan. Kans., May •_'<». L893, 
 spores from Callii'rhot alexoides, only a few germinations in forty- 
 eight hours; at Manhattan, June '.». L893, spores from ('. involucrata 
 germinated sparingly in twenty-five hours; at Manhattan. January 30, 
 1894, spores from ('. involucrata growing in greenhouse, fair germi- < 
 nation in sixty hours. 
 
 In the winter of L896-97 infected plants of ('. involucrata wore 
 obtained from Kansas and grown in a greenhouse at Washington, 
 D. C, and on March IT. L897, inoculations of seedlings of the follow- 
 ing grasses with spores from those plants failed to produce infections: 
 Agropyron occidentale, A. richardsoni, Sitanion elymoides, Elymus 
 canadensis, and Bovteloua racemosa. 
 
 Rust of Peucedanum Fceniculaceum. 
 
 An ^Ecidium occurs on this host in Kansas and Nebraska which lias 
 been reported as jE. anisotomes Reich., but the identity of which is 
 not yet determined" satisfactorily to the writer. At certain places a 
 Puccinia follows the .Ecidium so closely that their connection is very 
 probable. Both forms are particularly abundant at Manhattan. Kans. 
 On April 25, L893, at that place, it was determined by the study of 
 many cross sections of the host plant that the mycelium of the iEcid- 
 ium extends into the rootstock. Lt is one of the earliesl rusts in the 
 spring to appear in that locality. These facts make it probable that 
 this rust is also perennial. On the other hand, it is possible that the 
 teleutospores of the Puccinia ma\ produce a very early infection at 
 the base of the young shoots, resulting in the .Kcidium. although in 
 some localities no Puccinia has yet been found following the iEcidium. 
 
 «The species is probably Puccinia jorn sii I'k., with the tecidial stage present. 
 
i:i 3T OF PEUCEDANUM bXENICl LA< El M. 29 
 
 At Lincoln, Nebr., on March l'I. 1898, teleutospores of this same Puc- 
 cinia germinated in a water drop culture in twent} four hours. 
 
 It should be noted thai it is possible for a perennial rust to exist in 
 an annual li<>-t . the in\ tvlium of the rust being carried over winter in 
 the seed of the host. Such an instance is practically certain in the 
 Euphorbia rust already discussed. Granting thai Doctor Eriksson's 
 experiments were accurate, there would be another example in Puc- 
 ciniu glumarum Eriks. and rlenn. on svheat. 
 
PLATES. 
 
 ;;i 
 
DESCRIPTION OF PLATES. 
 
 Plate I. Frontispiece. A perennial rust. /Ecidium tuberculatum E. and K. on Cal- 
 lirrhoe involucrata < Jr. 
 
 Plate II. Fig. L. — Seedling of Euphorbia dentata grown constantly under bell jar 
 from rusted seed. Fig. 2. — Puccinia vexans Farl. on Bouteloua racemosa, both 
 uredosori and amphisori being shown. (Natural size.) Fig. 3. — The same ure- 
 dosori and amphisori shown in fig. 2 magnified LO diameters. Fig. 4. — Uredo- 
 spores of Puccinia vexans ■ 600. Fig. 5. — Amphispores of Puccinia vexans X 000. 
 Fig. 6. — Teleutospore of Puccinia vexans ■ 600. Fig. 7. Germinating uredo; 
 spore of Puccinia vexans ■ 300. Fig. 8.— Germinating amphispores of Puccinia 
 r, cans ■ 300. Fig. 9. — Uredosori of Puccinia vexans on young seedling leaf of 
 Bouteloua racemosa produced by artificial infection with uredospores from t lie 
 same host, i Natural size I. 
 
 32 
 
 o 
 
Bui 63. Bureau of Plant Industry, U S Dept of Agriculture. 
 
 Plate II. 
 
 Rusts of Euphorbia and Grama Grass. 
 
[Continued from page 2 o( cover.] 
 
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