By Willard N. Clute.
Living as I do in the midst of a region rich in specimens of the ternate
_Botrychiums_, I have taken more than ordinary interest in the
discussion of the relative rank to which the various forms should be
assigned. After considerable study of the subject which has consisted of
a careful balancing of the degree of differentiation in each form, as
well as an examination of much material both in the herbarium and in the
field, I have come to certain conclusions which I purpose to set down
here.
Before the separate forms are discussed it may be well to say a few
words on the variations of _Botrychium ternatum_ in general. It is a
noticeable fact that all the so-called new species of this section of
the genus, have been based primarily upon the cutting of the sterile
part of the frond. This is all the more remarkable since there are
probably no other genera in which species are founded on the minor
outlines of a mere leaf. One has but to turn to nature in any clime to
see that leaves are not invariably of the same shape. Note the wide
variation in the moonseed, the hollyhock, the sassafras, and some of the
buttercups among flowering plants, and if it be contended that the cases
are not parallel, take as further illustration the blood-root, which,
like the _Botrychium_, produces but one leaf a year, and note the
cutting of its single leaf. If all these forms of _Botrychium_ are
species, why have not the forms of the bloodroot been segregated?
Moreover, if we are to recognize these forms of _Botrychium_ as species,
why should we not also recognize as such the three hundred forms of
_Athyrium filix-foemina_, or the hundred or more forms of
_Scolopendrium_? It is unavailing to say that these latter are mere
gardeners' varieties, for we have it on the authority of Mr. Druery, who
is familiar with them all, that a large number come true from spores.
Experiments with flowering plants have shown that the thickness of
leaves and the amount of cutting of their edges, may be altered by
different degrees of moisture, sunshine, etc., to which they are
exposed, and we may infer as much for the ferns. This being so, it is
not difficult to account for the slight variations in cutting exhibited
in plants from widely separated points in the United States.
It is, of course, possible to follow the latest writer on the subject,
and consider each extreme of variation a distinct species, but I do not
agree with him in the opinion that the naming of varieties is a stupid
practice, nor do I see that it necessarily follows that because a
species was named _Japonicum_ from Japanese specimens that we must infer
that its centre of distribution is in Japan. As I understand it, to take
a familiar example, _B. ternatum_ stands for a plant possessing certain
characters no matter where found. If we should find another _Botrychium_
that differed from this in some specific way, it would be correct to
call it another species; but if it showed minor differences, slightly
thicker or thinner leaves, a longer or shorter stipe, a little deeper
notching of the leaves, etc.--all characters that vary with the
locality--then it would seem more properly referred as a variety of the
first species.
As I have noted in this journal there are certain slight differences
between the Japanese _B. ternatum_ and our familiar species of Eastern
America, but these are not enough, I now believe, to make them two
separate species, since all the differences are found in the texture and
cutting of the sterile part of the frond. Under such circumstances I
would arrange our American forms as follows:
Botrychium ternatum obliquum (_B. obliquum Muhl._). The common form in
the North Atlantic States.
B. t. obliquum forma DISSECTUM (_B. dissectum_ Spreng.). An exact
duplicate of the preceding form in everything except the cutting of the
pinnules. These latter characterized by a paucity of tissue between the
terminal veins. Has the same habitat and range, and the same peculiarity
of waiting until July or later before putting up its leaf for the
season. No more entitled to specific rank than the "cut leaved" birch or
elder.
B. t. obliquum forma INTERMEDIUM (_B. obliquum intermedium_ Unde.). I
would call this a mere form, comparable to any of the chance varieties
of _Athyrium filix-foemina_.
B. t. obliquum forma COULTERI (_B. Coulteri_ Unde.). A western form
rather more fleshy than that of the East. Grows in geyser formations
which may account for the difference in its appearance.
B. t. obliquum forma OCCIDENTALE (_B. occidentale_ Unde.). Closely
related to the preceding, and, in my opinion, a phase of it. Both good
representatives of the western form.
B. ternatum Oneidense (_B. ternatum_ var. _Oneidense_ Gilbert). This,
the most strongly marked of the forms in the Atlantic States failed to
receive a place in the recently published index to the described species
of _Botrychium_. It can be distinguished at a glance in field or
herbarium by its broad and slightly divided pinnules, and is very common
in central New York. The fronds, notwithstanding their broad pinnules,
are among the smallest of the group. If any of our forms of _Botrychium_
are entitled to sub-specific rank, this is certainly the one.
B. ternatum silaifolium (_B. silaifolium_ Presl.). This is also mainly a
western form. To it, however, I would refer the plant recently described
by Mr. Gilbert as _B. obliquum Habereri_ from central New York. I have
examined the type specimen and in my opinion it agrees perfectly with
specimens of _silaifolium_ from California identified by Dr. Underwood.
Even the striations produced in the pinnae by drying appear identical. I
should call this a sub-species, as it does not approach the type as
closely as the others.
So little is known about _B. biternatum_ Unde. and _B. tenuifolium_
Unde. that I shall not attempt to place them. Judging from what I have
seen of the latter, and I have seen numerous plants in the field, I
should consider it a form of _obliquum_ and I suspect that _biternatum_
will prove to be based upon aberrant plants of this which have fruited
in spring instead of autumn. In regard to this, Mr. W. W. Ashe has
recently informed me that many spring-flowering southern plants do not
flower in the North until late summer. It is possible our ferns may have
similar changes in their fruiting season.