340 PLANT STUDIES 
sporangia, which produce spores of but one kind, hence 
these plants are homosporous ; and as the sporangia origi- 
nate in eusporangiate fashion, Equisetum has the homospo- 
rous-eusporangiate combination shown by one of the Fern 
groups. It is interesting to know, however, that some of 
the ancient, more highly organized members of this group 
were heterosporous, and that the present forms have dioe- 
cious gametophytes. 
LYCOPODIALES ( Club-mosses) 
221. General characters, This group is now represented 
by about five hundred species, most of which belong to 
the two genera Lycopodium and Selaginella, the latter 
being much the larger genus. The plants have slender, 
branching, prostrate, or erect stems completely clothed 
with small foliage leaves, having a general moss-like ap- 
pearance (Figs. 306, 307). Often the erect branches are 
terminated by conspicuous conical or cylindrical strobili, 
which are the " clubs " that enter into the name " Club- 
mosses." There is also a certain kind of resemblance to 
miniature pines, so that the name " Ground-pines " is some- 
times used. 
Lycopodiales were once much more abundant than now, 
and more highly organized, forming a conspicuous part of 
the forest vegetation of the Coal-measures. 
One of the distinguishing marks of the group is that the 
sperm does not resemble that of the other Pteridophytes, 
but is of the Bryophyte type (Fig. 277) ; that is, it con- 
sists of a small body with two cilia, instead of a large 
spirally coiled body with many cilia. Another distinguish- 
ing character is that there is but a single sporangium pro- 
duced by each sporophyll (Fig. 306). This is in marked 
contrast with the Filicales, whose leaves bear very numer- 
ous sporangia, and with the Equisetales, whose sporophylls 
bear several sporangia. 
