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\C0

(From the Canadiak Jovrval for Nowtnber, 1866.;

ON CHORISIS.

A3 AK EXPLANATION OF CERTAIN 'VEGETABLE 8TH,.V>rnj»«g.

BY THE REV. WILLIAM HINCKS, F.L.S., F.B.'s. EDkN.,

■OV. HBHBBB 0» THB LITBBPOOt tIT. i.HD PHII,. 80C TORKBn PWir mnn .<«. .-. .
0» CAHADA, COBBKSPONDIirS MBMBEB o/thB BMBX TO JSsTWnTM^wn ^i-"***
BVIFALO BAT. HI8T. SOC. PE0FBS80B OF BAT."S CBXV COlt " OM«o"

I n

, It has of late years, been the aim of philosophical botanists to estab-
lish a few general laws of vegetable structure, capable of explaining all
the phenomena which fall under our observation, so as to exhibit a
eonamon plan in all the various fosms of plants, and show the kind of
variations from the general type which occur in each particular in-
stance, or in other words, to trace to the action of intelligible causes
the peculiarities observable in each distinct structure, so as to show
what is common to many, and how mutual relations are manifested ia
the midst of apparent diversities. This is, perhaps, to be accounted
the highest and most interesting part of the study of nature, and if it
must necessarily be preceded by the examination of the details of in-
dividual structures, always varied, curious, and attractive, it at least
anses out of them as naturally as the philosophy of every science
arises out of its facts and observations, combined and meditated upon
by the highest intelligences amongst its votaries, aided at times by the
happy thoughts of humbler labourers injthe same field. I design now

W^'

2 ON CHORISIS.

to bring under consideration one of the principles which has been pro-
posed as a general expression of a number of facts in the structure of
flowers, or, as a cause which may be assigned in explanation of some
remarkable features belonging to particular flowers, explaining at once
the relation to the common plan, and the meaning of the apparent
descrepancy in the special case.

My subject is what was, I believe, first named by the French botan-
ist Dunal, chorisis, a Greek word expressing division or separation&nA
applied to supposed cases of a single organ in a floral circle being, so
to speak, resolved by subdivision into a number of parts. At present,
whilst many high authorities admit this principle as affording the true
explanation of some remarkable facts in the structure of certain flowers,
other authorities of not less general weight entirely reject the principle
as unsupported by any sufficient evidence, and not needed to explain
the phenomena. In such a case any contribution towards determin-
ing the point in dispute may be received with patience and may have
some claim to attention. It may be expedient in the first place to con-
sider what are the principles in relation to^the structure and variation
of flowers which may be regarded as known and established, and to
what extent they go in explaining* the appearances before us that we
may be prepared to judge how far further assistance is required, and,
if so, how far the proposed principle sup)>lies what is wanted : nor will
this view of what may be said to have been accomplished in an im-
portant field of enquiry be in itself destitute of utility since compara-
tively few years have changed the whole aspect of botanical science^
and our greatest practical botanists continue to employ in decsription,
terras founded on erroneous opinions, and suggesting false vi-ws v^ere
on so many accounts the utmost correctness of language is denv. ?(\,
besides that the truths to be enumerated, though well established and
admitted by those esteemed the best judges, are by no means so gene-
rally received and applied as not to require to be explained and en-
forced.

The 1st principle to be noticed is that every flower originates in an
ordinary bud modified in its development, the increase of the axia
being checked and the leaves reduced into circles and made to assume.
the characteristic forms of floral organs, which setting aside interme-
diate end anomalous ones are 4, described and named as follows : thft
exterior one, usually retaining most of the leafy charactergCalled as a.
whole the calyx, and its separate organs named sepals : within it an-

ON CHORI8IS.

other set of protective or enveloping parts, usually of a more delicate
texture, and more likely to be colored, called the corolla, and its parts
petals ; then a set of organs so transformed as for the midrid to be-
come a simple support called Wie filament, the lateral expansion to be
contracted into cells forming the anther, whilst the superficial cells of its
infolded surface are specialised into sperm cells called pollen. These
organs as a whole are called androecium and singly stamens. In the
remaining circle the leaves are made to bear on their margin or at their
base germ cells called ovules, this expanded portion of the leaf or of
several such leaves united being the ovarium ; the apical portion gene-
rally drawn out to some length, is the style, and the naked glandular
tip is the stiffma. The whole circle of these leaves is the gynoecium,
individually they are carpels. As there are four distinct modifications
of leafy organs, forming in typical examples as many circles, there is a
manifest convenience in having a name for each circle as a whole and for
the parts of each, besides any names required to designate special por-
tions of each organ. I have adopted names from good authority
using care in their selection. The chief thing to be observed is the
use of the term gynoecium for the whole of the inner circle and car.
pel for each separate part. I have judged it necessary to reject en-
tirely the Linnaeau term pistil, because, the true theory of the struc-
ture of the flower not being then understood, he used the term, some-
times for the whole circle of carpels when so united as to seem a single
organ ; sometimes for each separate style where the ovarian portions
of the carpels are united, but their styles distinct, and sometimes for
each carpel where they remained entirely separate, the word is useful
enough in reference to the Linnsean artificial system, but cannot be
employed to express what is now known without being a source of
confusion. It is much to be regretted that eminent teachers of the'
science will persevere in employing it, especially as the evil is greatly
aggravated by attempts to give the term a new meaning or to persuade
us that Linneeus employed it in accordance with our modern ideas.

2. Havinj, considered what seems well established, respecting the
origin of the flower and the nature of its parts, what first claims our
notice is the variation in the number of circles.

We have mentioned four differing in kind, but we may have one,
two, or three of these absent, and we may have them increased by the
occurrence of many circles of one kind of organ. The difference is in
the development of the axis of the flower, which varies from a single

W{\

■ m

ON CBCRI818.

circle to an indefinite number, the increase being chiefly in the inner
ones. Whenever a flower preaents a crowd of similar organs, whether
manifestly in successive circles, or by their closeness thrown into a con-
fused mass, the explanation which first occurs to the botanist is multi-
plication of the circles, whether there may be sometimes reasons for
rejecting this and seeking another may be afterwards considered.

8. Our third principle relates to the position of the circles. The
most natural and general is with the parts of each (the numbers con-
forming) alternate with those of the circles without and within it. This
evidently depends on the same spiral plan of growth which produces
'the arrangement of leaves on a stem, the members of the successive
circles being indeed produced in the same plane, but when some growth
becomes necessary to obtain space for another circle, the advance of
the axis being as usual spiral, and to a degree just sufficient to make
the parts alternate, but besides that a whole circle may be so nearly sup-
pressed by close pressure, as to be scarcely, if at all, perceptible, which
would make those immediately within and without appear opposite,
the alternation being maintained by the unnoticed intermediate circle,
•which is doubtless the true explanation of the stamens opposite to the
petals in the Primrose family , it is quite conceivable that in certain
^ases the spiral course might be either prevented, or carried too far for
alternation, the parts thus becoming opposite and abnormal examples
occurring in which this is seen to take place, proves that we are justi-
fied in assuming it as a sufficient explanation of the rare instances in
"which adjoining circles with opposite parts occur. Dr. Lindley has
justly appealed to varieties of Camellia, in which the petals are ranged
in regular lines, giving the flower a star-like aspect as proof of the
possibility of the opposite arrangement taking the place of the alter-
nate, and those who think otherwise are driven to the most extrava-
gant suppositions to evade the force of his argument. But I must af-
terwards recur to this subject in another connection. At present I
wish to show the real nature of the law of alternation, and the possi-
bility of deviation from it in exceptional cases, without disturbing our
idea of the plan of structure or driving us to imagine other causes in
operation.

4. The degree and mode of development of the separate leafy organs
which form each circle may vary from the smallest to the fullest ex-
tent, and through several remarkable differences of form. All the
parts of the flower consist of leaves modified in their devolpment, and

ON CHORI8I8. fC

each is capable of assuming any of the functions, for we have mon«
strous examples (and I quote none but what I have seen) of carpels
occurring among the exterior parts of a half-transformed bud, petals
and imperfectly-formed stamens being found within ; of stamens with
anthers present having stigmas at their tips and imperfect ovaries at
their lower portion ; of petals and stamens passing by all degrees intoi
each other and of all the circles returning to leaves. Besides these
there are well-known intermediate conditions such as used to be called
nectaries, and besides the expanded or unfolded condition of an organ,
tubular, hooded, and spur or horn-like enlargements are not unfrequent-
ly met with. The leading effects of varying development may, in ad-
dition to what has been already pointed out, be conveniently noticed
under the following heads, connection or separation of parts ; equality
or inequality of the parts of a circle, and influences on the number of
parts. As to the first of these, it is a law of vegetable structure, that
portions of growing plants, whether of the same, or of closely allied
kinds, being in contact and continuing so, for a time without agitation, .
will form tissue so as to unite and become as one. This law prevails
in the parts of flowers as elsewhere. The result is coherence when or-
gans of the same circle unite by their edges, adherence when organs of
adjoining circles unite by their surfaces. Increased development of
the parts promotes coherence ; closeness of the circles promotes adher-
ence, and differences in these particulars have much to do with the
variations of the common plan of flowers.

We need not, however, be in any doubt as +0 the true explanation of
what occurs, as we are familiar with cases of degrees of coherence from
the slight attachment of the petals of a Flax or Woodsorrel to the
complete union of these parts in a Convolvulus or an Erica, from the
connection of the petals at the base only in some cases, to its reaching
the very tip in others, and we may have seen a little starvation restore
a Bellflower or Convolvulus to five separice petals.

It is necessary, to be able to express what happens in precise and
accurate language, and as the terms monosepalous, monopetalous, af-
firm what is well known not to be true, and are fitted to obscure the
ideas of students, whilst DeCandolle's terms, gamosepalous, gamope-
talotis, are figurative and too long, and have met with liMle aceept-
ance, I take this opportunity of -proposing terms long used by me,
as a teacher, which seem fully to supply what is needed without being
liable to objection. Let tlie coherent parts be called synsepalotu,

.« I

ON CHORI8I8.

tynpetaloui, and if you please, synandroua, tynearpeUnus, whilst aepa>
ration may be expressed by apoaepalous, apopelaloua, jj-c. Adherence
•rises from pressure of the circles on each other, or expansion of the
torus or receptacle, so as to adhere sometimes outward on the lower
part of the calyx, sometimes inward on the combined carpels, some-
times in connection with both, so as to place the fruit below the other
circles of the flower and produce the epigynose structure— it readily
explains many phenomena of common occurrence in flowers.

Regularity and irregularity of flowers depend entirely on the equal
or unequal distribution of nutrinieut to the parts of the successire
circles, the causes of which difllrences are often undiscernible, though
the fact is certain. Sometimes the more developed parts are in all the
circles on the same side of the flower ; in other cases the opposite sides
are enlarged alternately. In other instances the irregularity is produced
bv an opposite pair being enlarged in each circle (where the whole
number of parts is evenj, or by this arrangement being alternated in
the successive circles. It must be evident how many modifications of
flowers are explained by these considerations.

The primary law respecting number is found in the tendency to the
number three in the circles of mono-coty ledonous plants, and to five in
those of dicotyledonous plants. The first is an ultimate law of the
organization of plants abundantly established by fact, but hardly capa-
ble of being connected, so far as we can at present see, with anything
else we know of their nature. It may be doubted whether the second
is not connected with the first in as much as one cotyledon or primor
dial leaf is found to imply a circle of three parts, two would therefore
be expected to produce six, but this supposes the combination into
one of two circles of three. Now we have other examples of this sort
of combination of circles of parts exhibited to us by certain anomalous
flowers, in sufticient number and variety of cases to suggest a sort of
rule as to what is likely to happen, and from them we infer that in
ordinary cases one part would be lost in the union. That under con-
fiiderable pressure a part would he lost at each point of junction or two
in the combined circle, whilst very close position, with circumstances
unfavourable to development, such as give us occasional examples of
two and oue part in a monocotyledonous plant might occasion any of
the lower numbers to occur in a dicotyledon. I found the exj)lanation
here given of the prevailing number of dicotyledonous plants on the
careful examination of a considerable number of those monstrosities, not

• V

,li

ON CHOK18IS. 7

of very uncommon occurrence, in which two flowers nrc combined into
one from their origin, owiiiK to their buds having been adjacent. I can
now distinctly recall examples in two or three species of Iris, and in at
least three speciesofOenothera, my cultivation at one period of numerous
species of those genera affording me (he opportunity of observing the
anomalies to which they are liable. I had various instances of circles
of five in the monster Iris and of seven in the Oenothera— one instance
of four in the Iris in a single circle and one of only three, the exterior
circles having five, and the tube showing sufficient marks of the union.
In the Oenotheras observed, which embraced several species, there were
uniformly seven parts in each circle, that is, seven sepals, seven petals,
fourteen stamens and seven carpels. I gave some account of these
monstrosities to the Linnoean Society in 1 839, and it has since occurred
to me that they establish a law respecting the combination of circles
of growing parts, which may explain the tendency to the number five
In Dicotyledonous plants, since, when growth is carried on from a single
cotyledon, we find the number three in the circles, and where there
«re two cotyledons we might expect the circle to be double, but the
fact of the loss of at least one part in combinations of two circles on
the same plane shows why the number five takes the place of six.
The liability of the natural numbers, five in Dicotyledonous and three
in Monocotyledonous, to be reduced by mere pressure or by irregu-
larity, is obvious from what has been already said. We find by obser-
vation that the number of parts in the successive circles of the flower
is usually equal, but that the inner circle, being exposed to greater
pressure, is apt to have fewer than the others — three and two carpels
being very common in Dicotyledonous plants. In some structures
the numbers in the different circles do not at all correspond, but tiiis,
which is characteristic of particular families, is less common, and its
origin is one of the most obscure and dubious points in the theory of
the flower. When parts are absent either from pressure or irregu-
larity, we must remember that the fact is due to a special cause of
abortion, not to the total absence of the i)art from the structure, and
consequently that circumstances may occur from more abundant or
equally distributed nourishment, which may in anomalous examples
restore the missing part. Such examples are, nideed, almost needed to
confirm our judgment as to the causes of the ordinary absence of these
parts, and have therefore great interest for the philosophical botanist.
In the natural family of the Onagraceze, to which the genera Fuchsia

f I

ON CHORI8II.

and Oenothera belong, the reduction by pressure of the natural num-
ber to four instead of five, and sometimes to a smaller number, is char-
acteristic, but it is by no means uncommon to observe the restoratioi
of the fifth part ia both Fuchaias and Oenotheras under high culture
and, when it occurs at all, it takes place uniformly through all tha
circles. I have seen various examples in both genera. In the great
order Fabaceie, the Leguminous plants, a single carpel from abortion
through irregularity of the rest of the circle is characteristic, but I
have often met with kidney beans with two opposite carpels united by
their edges so as to remind us of the maple fruit, and ia Acer Pseudo-
platanus, the Sycamore, I have found, instead of the usual pair of
earpels, a complete circle. We are thus forced to admit that tha
parts deficient in particular structures are absent through abortion,
but were rudimeatally present in the bud, capable under favourable
inlluences of being developed.

In fact the number five is very common in the exterior circles of
Dicotyledonous plants, less so ia the gyncecium, though often occur-
ring there nlao; four is often produced both by pressure and by
irregularity, three is occasionally found, and two rather more fre-
quently, whilst in cases of the least amount of development, where the
circles are reduced to two, or even one, a single organ in that circle is
all that appears. In monocotyledonous j)lants the number three, and,
from additional circles, its multiplies, is somewhat more constant, but
abortion or degeneracy of organs from irregularity, is found through-
out the Musal and Orchidal alliances and in grasses ; and other irrei'U-
larities of number occur. Our general laws of Floral structure, once
understood, leave little difficulty in recognizing the proper explanation
of the facts as they fall under our notice.

Having now shortly reviewed those principles which m;>y be regarded
as admitted among those botanists who apply themselves to the theo-
retical relations of the flower and its organs, tracing what is common
and accounting for what is varied in the different structures, and hav-
ing ventured to add one or two suggestions for improving these views
or the mode of expressing them, we are prepared to estimate the evi-
dence for any additional principle, where we have to judge whether the
phenomena are susceptible of good explanation by the aid of those
already established, or really require some new generalization for the
correct expression of what occurs, and the perception of its true rela"
tions with other facts — and then whether the proposed principle agrees

ON f '^CRIBIt. «

with and htrmonisM all the facta ao aa to be received aa what we call
a geod explanation of them. The kind of facta which thon»i» under-
takea to explain are cases in which the avmiretry of the flower as
commonly understood would suggest the expectation of one organ
hot we actually find two or more, and these in an unusual d-gree of
proximity; cases in which the multitude of apparently distinct organs
produced in close proximity seems inconsistent with the supposition
of their belonging to succewive circles ; those in which a number far
exceeding the natural number seems to be found distinctly in one cir-
cle, and those in which a number of similar organs are combined at
their base in clusters, the number of clusters corresponding to what
might have been expected to be the number of organs. All these are
represented as being capable of explanation by collateral chorisis or the
■ubdivision laterally of one organ into e. number of organs. There is
alf a different class of facts, such as the occurrence of organs arising
ou the face of other organs and opposite to them : sometimes of lines
of opposite organs, which bping supposed inconsistent with other
principles of structure, are explained as cases of transvenc chorisis,
or the division of a single organ into folds like the splitting of a card
into two or even many similar or related organs. It cannot be denied
that the cases to which chorisis has been applied as an explanation are
attended with some difficulty, and that some of them are even incapa-
ble of plausible explanation by previously established principles-
Some of them, however, appear to me quite consistent with those prin-
ciples, as I shall endeavour to show when examining some alleged
examples, and although it cannot reasonably be affirmed that such an
operation as chorisis is inconceivable as arising from the nature of the
organs of the flower, and it seems even to be sanctioned by some facts,
yet I find myself obliged at least to limit its application within much
narrower bounds than some able botanists have assigned to it. My rea-
Bona will be best given in an examination of the particular cases brought
forward at least a sufficient number of them to justify a general opinion
on the subject. I shall take the examples given by Dr. Gray, who
adopts fully the theory of chorisis in his valuable work, the Botanical
Text Book. pp. 250-2.55, having reference also to his remarks in •• The
genera of the United States Flora, illustrated.'* Dr. Gray's first ex-
ample of collateral chorisis, on which he is disposed greatly to rely, is
found in the Tetradynamous stamens of the natural family Bramca-
ee<B. This case I considered at large in a paper read before the Cana-

m I

f«

ON CHORISIS.

dian Institvte in Fcby. I860, and published in Vol. V. of the "'Jour-
nal, p. 382, to which I now refer. I accept the quaternary symmetry
in Brassicaceae, but consider the two lower stamens as part of an ex-
terior circki of which two glands frequently present represent the other
two members. I see no pretence for regarding the two pairs of stamens
as ea'"h representing one divided organ, and I explained in consistency
with my own view all the facts produced. Dr. Gray's second exam-
ple is found in the androecium of Fumariaceac. This consists appar-
ently of six stamens in two groups of three each, and Dr. Gray regards
them as really two organs, each dividqd into three by collateral chorisis.
It is to be observed that the two lateral stamens of each group have
one anther each, while the central one has two. This suggested the
theory of DeCandoUc, supported by Lindley, that there are really two
pairs of stamens, but those which were in the direction of the lateral
pressure are split int*- halves, one half of each being pushed close to
the stamens of the other pair, so as to place the perfect stamen of each
end between two half stamens divided from the other pair. The Bras-
sicaceons moustrosity recorded in which an outer stamen is split so as to
resemble two each with a single anther, greatly supports this explanation
which is favored also by the separated anthers, one on each side the
column from the single stamen of many Orchidaceae and the instances
of widely separated anthers with a partially divided filament. On this
supposition there may be said to be a chorisis, but it is one of the most
intelligible kind as there is no creation of an additional anther or of any-
thing more than is present in the undivided stamen. It must be re-
membered that as chorisis is assumed to be a division from above, the
three stamens in Dicentra being often quite distinct below and only
coherent in the middle is very unfavorable to, I should almost say ab-
solutely inconsistent with Dr. Gray's theory, and whilst this example
is before us it is vain to appeal to ii\e more complete union in other
Fumariaceae, as it is an obvious case of coherence.

Dr. Gray's third example is one of those cases which appears to me
to justify the admission of the principle of chorisis as occasionally giving
us a satisfactory explanation of structures which without it seem in-
comprehensible. He refers to tlie three groups of stamens each com-
pletely united at their base in Elodea : justly observing that though
the two outer circles in this flower are pentamerous, the inner ones
three in number, the carpels, the three groups of stamens, and the
three glands are trimerous so that each group of three connected sta-

ON CHURI8I8.

mens represents a single organ. The same is true of the organs seem-
ingly representing abortive clusters of stamens in Parnassia, and the
ooservation of Duchatre as to the development of the numerous sta-
mens of Malvaceae from small protuberanres representing the single
stamens of the original circle may be confirmed by any one who wrill
examine with attention half-double Holyhocks in which intermediate
states are found between bunches of stamens and unfolded petals.

The close bundles of stamens in Ricinus and the fan-lik? groups
in some Myrtaceae may be of the same kind. Admitting then, the
principle to a certain extent, we need not multiply examples. The
difficulty is that, suj)posing the seattered parts of a vascular bundle
which forms the leaf to supply the filaments of a bundle of stamens,
we should anticipate the divided expansion giving only one cell to each
•nther, as is the case in Malvaceae, but in other cases referred to we
have two-celled anthers resulting from the divided leaf, a real difficul-
ty without doubt, yet not sufficient, perhaps, to overcome the reasons in
favour of the theory.

Transverse chorisis is quite a different thing and far more incredible
than what has thus far been discussed. The leaf of a Horse-chestnut,
a Virginian creeper, or a Lupin, occurs to us as a ready illustration of
the possibility at least of collateral chorisis, and it being satisfactorily
proved that an ordinary stamen is but a leaf developed under peculiar
circumstances, a leaf becoming a group of connected stamens cannot
seem entirely opposed to our reason, each portion of the leaf has its
own vascular bundle to form the filament and its own cellular expan-
lion to form the anther. But when we are told of that which is but a
thin lamella of organized substance, with its two surfaces differently
constructed, and its intermediate portion quite distinct from both,
splitting in planes parallel with its surface so as from the one
to produce a number of similiarly expanded organs possessing the
same general structure as the undivided organ would have done, we
may well exclaim against the extravagance of such an assumption, and we
try in vain to think of any thing which appears to justify it. A carpel
is but a leaf in a peculiar state of development, and as it advances
towards maturity as a fruit, we can often separate in a direction par-
allel with its surface three portions, the epicarp or outer surface^ the
mesocarp or vascular and intermediate portion, and the endocarp, the
inner lining of the fruit corresponding to the upper surface of the
ordinary leaf; but these three parts thong often separable in fact,

J^;

.^!; i,

M " 'i

J I

'iA

ON CBORISI8.

end always in idea could none of them exist as living parts without
the others, they are different portions of one organized substance, and
the consideration of the sense in which they are different, only the
more impresses us with the impossibility of supposing such elements
as would ordinarily produce one leaf, capable of producing, under any-
stimulus, many leaves standing in parallel planes, each containing all
the parts of the one. But it may, perhaps, be thought that there is
some other mode of representing this matter not liable to the prelimi-
nary objection here offered. Dr. Gray, who probably presents the
subject as judiciously and plausibly as any one has done, and whose
authority would justly go as far as mere authority ever can, is disposed
to treat the question as one of fact, as if he said : it cannot be denied
that examples occur of multiplication of organs opposite to one another
in the flower which do not admit of explanation by their belonging to
successive circles — these facts claim consideration whether we can
explain them or not, but when stated, an explanation may be attempt-
ed — accordingly he begins by putting aside the theory t ^ which my
remarks above directly apply, in the words : " The name dedouhlt'
ment of Duval, which has been translated deduplication, literally
means unlining ; the original hypothesis being, that the organs in
question unline, or tend to separate into two or more layers, each hav-
ing the same structure. We may employ the word deduplication, in
the sense of the doubling or multiplication of the number of parts,
without receiving this gratuitous hypothesis as to the nature of the
process, which at best can well apply only to some special cases. The
word chorisis, also proposed by Duval, does not involve any such
assumption, and is accordingly to be preferred." He adds, respect-
ing transverse chorisis : " Some examples may be adduced before we
essay to explain them." I am myself disposed, nevertheless, to en-
deavour to understand and consider the theory proposed, and then try
its application to the facts. These facts are certain phenonena in
flowers which are, if possible, to be brought under general laws of
structure. Is it certain that laws previously known do not apply to
them ? and if this must be admitted is the hypothesis called transverse
chorisis the only possible one, and does it answer fully the require-
ments of the case ? These questions we can only answer when we
know what the hypothesis is — what supposition respecting the origin
of the parts is adopted. That of Duval is quite intelligible, and in tiie
case of collateral chorisis seems reasonable, applying well to some of

^I.

ON caoRisis.

4l.e e««, .„d .upported by «,m, good .ndogic. I„ r.,p.ct to tr«,«.
««. ehons,., u .ppe.™ to m, incoo,i.te„t with what i, k„own of
-epfble, lecture .ad. « Dr. Gray concede* unsupported by .oy
.ujlogy. But let u. i„,„ir. ,h.t .xpl.u.,iou Dr. Gray him.elf offe™
..d thei we can try hi, hypothesis by the facts. I regret that th"
Journal of Botany not being within .y reach at Toronto, I 11„
.ow recur ,0 the paper to which he refers. b«. the substance of h

..hom« .s found m the ligulc of grasses and the stipule, of other plant,
he doe, not think the supposition of axillary organ, in the pfatof
buds neces«ry. although he hold, that an ajlarv bud J uv

Ct't I ""t ':• '°'""*"' "' * ='"^" p'-X-d '„.•"*„ :

•organs in the situation expressed by transverse r},nn«;« tS .u"
impossible or ante.edently^ery i^pUab.e cTu be aH^ed'lli:?
these s«ppos..,ons Son,e recorded monstrosities even enflrZoJ

in some of the examples appealed to, and it is manifr.. XZ 'T^
^ould afford the smallest asltance in^xplai",:^ *' LT :'
..te organ, occurnng one within another; yel in replyT„7to "^or
Lmdley. argument, against chorisis. referring to his flS appeal
40 the case of certam varieties of Camellias in which the organs of sue
■eess-ve circle, become opposite, Dr. Gray says, "Xow whcir,!,.
Tery same .pecies, two such different mod's oV.rrangemenJ oc r •
.no. ,,„„„. „orc probable that the two arrangements resn f^^

inink not. The same organs are present in both cases ,nj „-.i,
^unnnition or a small increase in the spiral .endencv o grXth wo„U
ehange the usual alternation into the occasional oppositeness wiTholt
any thmg occurring at all inconsistent with known facts but n
OraywouidreceivetheoppositepctalsofthcseCamtS .'as'^n'^-
ple of transverse chorisis, it is at least one which hi. own IT i
explanation could not possibly reach, and which „„ aj; princTpl;:
proposed, must appear most extraordimiry. Let us now Z •! ^
few examples of transverse chorisis by wh'ich we m yTudgeTh tTeJ
c'ls^ "Ac'" "" ""■"^r "" -^ "- Fincip'.^ ap'pliX:
M. p. iij) „ that of the crcm or small and mostly two-lobed an
pendage on the .nside of the blade of the petal, of Si.cne Ind of man/ •

ON CIIORI8I8.

If!

other Cnryophyllaccous plants. This is more like a case of real df.
doublemont or unfinintf, a partial separation of an inner lamella from
the outer, and perhaps may be so viewed." But the close relation of
the petal to the stamen, and the many instances of a condition inter-
mediate between the two are well known, and it seems easy and natu-
r.nl enough to regard the crown as an imperfect development of anthers
whilst the expansion above it corresponds with the petal-like eiilart'e-
ment of the connective in some stamens, and the claw with the fila-
ment. Here then, we need no new principle, and find no real exception
to recognised laws. The appendage to the stamen in Larrea and other
Zygopliyllaceae is perhaps as good a case as can be found for the ap-
plication of the stipule theory which has here not a little plausibility,
although when we consider the modifications of development in a
single petaloid organ as shown in Eanuncnlns with its petal scales,
Helleborus with its nectariferous cup ; some species of Lilium with their
protrusions on the surface, and again the cases among the grasses of
awns which are the midribs of the glumes or paleoe to which they be-
long, departing at some distance below the apex, we, perhaps, ought
not to consider the appearances as inconsistent with the supposition of
one organ developed in an unusual manner. Perhaps the appendages
at the base of the anther in Erica are quite as strange as if they occur-
red at the base of the filament, and the stamen growing from the ex-
tremity of a petaloid process in Campanula not much less anomaloua
than if it rose from the same lower down, or at the base. Then we
have the stamen of Asclepias with its extraordinary appendages which
is as like the unlining of an organ as anything we are acquainted with,
yet undoubtedly is no more than a mode of development of the one
modified leaf.

The next example is taken from the genus Parnassia with its curioui
and beautiful appendages [nectaries of Linnaeus] opposite to the petals
immediately within them, and thence inferred to be derived from them^
or, as it were, a part of the same organ. These appendages may be
some justification of collateral chorisis though the multiplication of
parts is incomplete, but I confess I can find no reason for denying
them to be a circle of parts originating distinctly in the torus, although
they are placed opposite to the exterior circle. I have given reasons for
believing that oppositeness alone is no argument for identity of origin in
organs, and if it were, the fertile circle of stamens in Pamassia must
be accounted only a transverse chorisis of the carpels, as the membfira

ON CHOniilfl.

of the., two circles ,re ,I,o „pp„,cd to each other. The c.,e »f th.
group of ...„,c„, „i,h .he pctaloid aeale, behmd it io Le Zericl

..™e„,. .„„ „ ohaer,'e that ^1^:^ ^Z^:^T^

•nd „e h,.c a rcnarLhle ilte 2,2^^^^^^^ """""

curved in «,„re a, to produce the vcr, appelte Tlird ''" '"

These examples probably include all the varieties that wo„I,l IT i

takes the case entirely out of the foro^Ition of separa ! orL« ^ ^
explained on other principles, parSri; h Z^l ZT'^'"

Svedr^ihr.-:::;^^^^^^^

regularly set is no proof of chorisis. ^ '*°'^''''"

With these restrictions I receive chorisifi -^ »« „jj-.- i .
in the structure of flowers, afford nVusva^' f °'^ ^"""P^'^

them all. however varied. wUrgLeraltie^ ^
common relations. ^ ''' ^""^ "manifesting their