PTERID0PH7TA. 207 



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- 



Fio. 117.— Part of a Club-moss (Lycopodinm claTatum), the running, horizon- 

 tal rooting stem below, with the spore-bearing cones, s, above. One half natm-al 



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. 



