Isoetes melanopoda (J. Gay.) "Muddy borders of a pond near Hyde Park
water-works, 1885. Wet prairies near Grand Crossing, 1886-87."
_Higley_ and _Raddin_. These stations in Cook county are doubtless
destroyed now. Stark county, _V. H. Chase_. "Menard, _Hall_;
Fulton, _Wolff_; McHenry, _Vasey_." (P.)
Isoetes Butleri (Engelm.) "Moist hillsides and shallow depressions,
Illinois and Kansas to Tennessee and Oklahoma." Gray's New Manual
of Botany.
A PROBLEMATICAL FERN.
(_Gymnogramma lanceolata._)
By Willard N. Clute.
In the identification of fern species one occasionally comes upon two
forms so nearly alike that it requires very careful study to decide
whether they are two different species or merely two forms of a single
variable species, but it is rare that one finds a fern that can as well
be placed in one genus as another, and still more rare when the species
possesses characters so like those of ferns in other groups that it may
be moved from one tribe to another without violating any of the
botanical properties. The fern chosen for illustration here is one of
this latter character. It has been passed back and forth between various
genera in different tribes, seldom resting long in one place, until it
is a very problematical species indeed.
In outline and manner of growth it possesses no especial peculiarities.
The lanceolate leaves might fit any of a dozen or more species that
might be mistaken for it if the fruit dots or sori were absent.
_Vittaria_, _Taemitis_, _Antrophyum_, _Polypodium_, _Asplenium_,
_Acrostichum_ and many other genera have species with leaf outlines that
almost exactly match it, but a glance at the fruiting fronds, at once
excludes many of these genera as possible harbors for the species and at
the same time increases the difficulties of finally placing it. The sori
are apparently linear and _Scolopendrium_ or _Asplenium_ comes to mind,
but there is no indusium and so the relationship is thrown into that
group of ferns clustering about such forms as _Gymnogramma_.
In fact, our fern was for a long time known as _Gymnogramma lanceolata_
and owing to this fact I have selected this to stand as the name of the
plant. A glance at the illustration, however, will disclose a frond not
at all like the conventional _Gymnogramma_ frond, but it is as much like
a _Gymnogramma_ as it is like the family to which the plant is now
assigned. Curious as it may seem this plant with elongated sori oblique
to the midrib is now regarded as a _Polypodium_! Before its settling
down in this genus, it had been placed in _Antrophyum_, _Grammitis_,
_Loxogramme_ and _Selliguea_ as well as _Gymnogramma_. This is by no
means due to the variable nature of the fern. Through all these
vicissitudes it has remained unchanged. The fluctuations from one genus
to another even from one tribe to a different one, have been due to the
varying opinions of mere man and his efforts to fit the fern to a set of
descriptions of his own making. Circumstances such as these are quite
sufficient to justify the refusal to accept off-hand the results of
every "revision" which ambitious systematists see fit to inflict upon
us.
While reposing in the genus _Gymnogramma_, the fern was well-known to be
somewhat unorthodox. In every large assemblage of species there are, in
addition to those which are typical, certain others that diverge
somewhat, but not enough to form a separate genus. Thus our plant was
placed in the section _Selliguea_. Sometimes, indeed, _Selliguea_ was
isolated as a separate genus, but usually accompanied by the statement
that if it were not for the shape of the sorus it would make a good
addition to the section _Phymatodes_ of _Polypodium_. Here, at least, is
where it has landed, the elongated sori being winked at, possibly, or
perhaps the species makers are willing to assume each so-called sorus to
be a series of _Polypodium_ sori. In this age, however, there are those
who deny to the species in the group _Phymatodes_ the right to be
included in _Polypodium_ and in certain books our species appears as
_Phymatodes loxogramma_. Just how this _loxogramme_ came to supplant
_lanceolata_ is another story, not to be detailed here. Suffice to say
that the new name was picked up during one of the fern's numerous
transfers.
As to _Phymatodes_, it is likely that the species in this group are
distinct enough to form a genus by themselves but it would be a rash
student to encourage such a departure, for once started we should soon
see all the large genera cut up into lesser groups and then what
delightful times the name-tinker would have!
By what ever name called, the species manages to thrive over a wide
stretch of country in the Eastern Hemisphere, being found from Japan and
China to the Himalayas, Ceylon and the Guinea Coast and represented in
many of the islands of the Pacific including Fiji and Samoa. The
specimen from which the illustration was made was collected by K. Miyake
near Kyoto, Japan where it is reported "not so common."