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cell may be compelled to germinate in close contiguity, 
and are thus made to produce dense tufts of slender leaves. 
The latter explanation would be at once recognized by 
horticulturists as quite sufficient to account for the observed 
differences in habit among the plants. 
It 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 difficul- 
ties ; in fact, water and a little soil are the only requi- 
sites. 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 ; but the most interesting way in which it could be 
grown would be in an 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 be watched, and many interesting points 
of its economy could not fail to reward a careful 
observer. 
The aquatic-plant 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 
