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observed, the one having thicker, shorter, and more spreading
leaves than the other ; in the latter they are more slender and
erect. These have been thought distinct varieties or even
distinct species by some botanists, but are more probably
mere conditions of the plants brought about by external circumstances.
Several theories have been propounded as explanatory
of the way in which this occurs. Sir J. E. Smith
says, the taller, more slender variety may, perhaps, be caused
by those sudden risings of the waters so frequent in mountainous
countries, W'hich will account for all its peculiar
characters. Mr. Wilson believes the solitary plants with
short spreading leaves to be the first full development after
the seedling state, and before any lateral extension of the
rhizome has taken place ; and argues, that when the plants
become crowded, either by lateral increase or offsets, or by a
multitude of individuals in close contact, the fronds can only
grow erect. Mr. Newman thinks, that when the seeds arrive
at maturity, the leaf in whose base the spore-case is situated
decays and becomes torn or broken off, allowing free egress
to some of the spores, which become dispersed, and produce
the isolated dwarf spreading plants. Others and by far the
larger number of the spores do not become thus disengaged,
and are compelled to germinate in the capsule, throwing up
most dense tufts of slender leaves. MTthont having made
any critical observations on this point, we decidedly prefer
Mr. Newman’s explanation, which, as would be at once recognized
by horticulturists, is quite sufficient to account for
the observed differences in habit among the plants.
I t is said that fish feed on the Isoetes ; and that, when
brought within the reach of cattle, it is greedily eaten by
them, and proves fattening.
The cultivation of the Quillwort presents few difficulties ;
in fact, water and a little soil are the only requisites. In
such a miniature lake as has been recommended to be introduced
in a Wardian case fitted up for Club-mosses, this
plant and the Pilularia might be made to thrive; hut the
most interesting way in which it could be grown would be
in ail aquatic plant-case, with transparent sides, or in any
substitute for such a structure, such as a glass jar of sufficient
depth. Planted in this way, its growth could he
watched, and many interesting points of its economy could
not fail to reward a careful observer.
The aquatic plant-case, like the Mfordian case, admits of
much variety of detail. The most useful form is probably
that of a rectangular glass cistern of the requisite size, held
together by a light metal frame, and closed in by a glass lid.