CHAPTER VIII 
PTERIDOPHYTA — Concluded 
BESIDE the true ferns there are two other classes of 
existing Pteridophytes, —the Equisetinee (horsetails, 
scouring-rushes) and the Lycopodinee or club-mosses. 
The former, while showing certain points of resem- 
blance to the ferns, still differ so widely from them that 
they are properly included in a separate class. All the 
known living forms belong to a single genus, Equise- 
tum, which comprises about twenty-five species, mostly 
belonging to the northern hemisphere, and especially 
well represented in the United States. The peculiar 
sporophyte (Fig. 86, A), with its jointed, grooved stems, 
and sporiferous cones, is familiar to every botanist. 
The gametophyte is less generally known and shows 
many points of resemblance to that of the ferns, espe- 
cially the Eusporangiate. The green spores germinate 
promptly if sown as soon as they ripen, but soon lose 
their power of germination. After about a month the 
male gametophyte is mature, the female plant requir- 
ing a somewhat longer time. In its earlier stages the 
gametophyte is much like that of the common ferns, 
but is more irregular in shape, developing more or less 
definite lobes, which are especially conspicuous in the 
female plant. The growth of the latter is a good deal 
like that of the gametophyte of Marattia or Osmunda, 
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