XIII 



LYCOPODINEAi 



493 



appear above the surface of the earth until several years have 

 elapsed. The leaves developed u])on these sujjterranean shcjots 

 are rudimentary. Sometimes mcjre than one s])(jr(jphyte is 

 borne by the prothallium (Fig. 284, B). The differentiation 

 of the vascular cylinder beiGi'ins about the time tliat tlie root 

 breaks through the prothallial tissue. The hypocotyledonary 

 part of the stele is diarch, but higher up four or five protoxylem 

 groups are developed. 



Fig. 286. — A, Lycopodiiim pachystachyon, X}i; B, L. volubilc, showing the two forms 



of leaves, X2^. 



The Adult Sporophyte 



In all species of Lycopodium the sporophyte possesses an 

 extensively branched stem, which may be upright, as in L. 

 cernuiim, or extensively creeping, as in L. clavatuui and other 

 species, where the main axis is a more or less completely sub- 

 terranean rhizome with upright secondary branches. In the 

 tropics some species are epiphytes. The leaves are always 

 simple, and of small size. Each leaf has a single median vas- 

 cular bundle, which does not extend to the apex. The ar- 

 rangement of the leaves is usually spiral, and they are uni- 

 formly distributed about the stem, and all alike ; but in a few 

 species, e. g., L. coinplanatuui and L. volubilc, they are of two 



