L TCOPODIN^E. 



383 



bears both kinds of sexual organs. In the heterosporous 

 genera the macrospores produce small prothallia, which 

 project slightly through the ruptured spore-wall, and upon 

 these several or many archegonia are formed ; the micro- 

 spores produce very small rudimentary prothallia, each of 



FIG. 274. 



FIG. 275. 



Fig. 274. .4, longitudinal section of a young prothallium of Lycopodium anno- 

 tinum ; an, two antheridia ? not mature upon its lower surface are seen the root- 

 hairs, x 150. B, longitudinal section of a prothallium, p, of the same, after germi- 

 nation of the young plant ; , stem of young plant ; r, its young root ; /, the foot, or 

 portion of the young plant which remains in contact with the proihallium. Slightly 

 magnified. After Fankhauser. 



Fig. 275. Plant (asexual generation) of Lycopoiium clavatum; horizontal stem 

 with roots and leaves, the erect branch bearing fertile spikes, . One half natural size. 

 After Prantl. 



which bears a single antheridium, in which there are de- 

 veloped a few spermatozoids. 



494. Three orders of Lycopodinae may be distinguished, 

 as follows : 



/. Isosporece. Spores of one kind ; no ligules. 



Order 1. Lycopodiaceae, with small leaves, commonly 

 moss-like. 



//. Heterosporece. Spores of two kinds ; ligules present. 



Order 2. Selaginellse, with small moss-like leaves. 



Order 3. Isoetese, with elongated grass-like leaves. 



