xiii LYCOPODINEJE 485 



leaves, though usually numerous, are simple in structure and 

 generally small. The genera are all homosporous except 

 Selaginella, which is very markedly heterosporous, and has the 

 gametophyte very much reduced and projecting but little be- 

 yond the spore wall. 



CLASSIFICATION 

 Order I. Lycopodiales 



A. Homosporece 



I. Roots always present ; sporangia alike, simple, in the 

 axils of more or less modified leaves, which may form a distinct 

 strobilus, or may be but little different from the ordinary ones 

 both in form and position ; prothallia either green or colourless, 

 monoecious. 



Family I. Lycopodiace^ 

 Genera 2. — (i) Lycopodhmi; {2) Phylloglossuni 



II. Roots absent ; vegetative leaves much reduced or well 

 developed; sporophylls petiolate, bilobed; sporangia pluriloc- 

 ular; gametophyte unknown. 



Family II. Psilotace^ 

 Genera 2. — (i) Psilotnm; {2) Tmesipteris 



B. Heterosporece 



Characters those of Family L, but spores always of two 

 kinds. 



Family III. Selaginellace^ 



Genus i. ^ Selaginella 



THE LYCOPODIACE^ 



The Gametophyte 



The Lycopodiacese include the two genera Lycopodium 

 and Phylloglossuni, the latter with a single species, P. Drum- 

 mondii. The gametophyte is known in a number of species 

 of Lycopodium, and recently (Thomas (i)), has also been 



