PTERIDOPHYTA, 907 
genera the spores are of one kind; while in others they are 
of two kinds, large ones (macrospores) and small ones 
(microspores). 
436. The first stage (prothallium) is but little known in 
the genera with one kind of spore only; it appears, how- 
ever, to be a thickish mass of tissue, which develops under- 
Fie. 117.—Part of a Club-moss (Lycopodium clavatum), the running, horizon- 
tal rooting stem below, with the spore-bearing cones, s, above. One half natural 
size. 
ground, and bears both kinds of sexual organs. In the 
genera with two kinds of spores, the macrospores produce 
small cellular growths, which project slightly through the 
ruptured spore-wall, and upon these several or many arche- 
gones are formed; the microspores produce very small, few- 
celled growths, each of which bears a single antherid, in 
which there are developed a few antherozoids. 
