PTEBIDOPHTTA. 209 



are all of one kind, and are borne in roundish spore-cases, 

 ■which are generally single on each leaf. 



The Club-mosses are commoa in the Appalachian region, Canada, 

 and northwestward, and all but one of our species belong to the 

 genus Lycopodium. Of these may be mentioned the Common Club- 

 mosses (L. clavatum and L. complanatum) and the Ground-pine (L. 

 dendroideum), all extensively used in Christmas decorations. 



438. The Little Club-Mosses {Order Selaginellaceoe) re- 

 semble the foregoing, but are generally smaller and more 

 Moss-like, and have (-with few exceptions) four-ranked 

 leaves. Their spore-cases occur singly on certain more or 

 less modified leaves, which are clustered into terminal 

 spikes. The spores are of two 



kinds; the small ones, which are 

 very numerous, are generally 

 borne in spore-cases in the upper 

 part of the spike, while the 

 larger ones (macrospores) are 

 mostly four in each spore-case in 

 the lower part of the spike (Fig. 



118). FiQ. 119.— Plantlets of a Little 



. „ mi /> , , <• 1 Club-moss (Selaginella martensii), 



439. The Iirst stage OI the showing cotyledons. J.twoplant- 



. lets growing from one spore; p, 



Little Club-mosses is almost ob- "le first stage (prothalUum). II, a 



plantlet separated from the spore; 



literated. "When a small spore Xi^^f.,) -^ * nifled'"™ " *^* 

 germinates, it becomes divided 



internally into a considerable number of cells, one of which 

 appears to represent the first stage (prothallium), while all 

 the rest form one large antherid, each cell of which pro- 

 duces an antherozoid. 



440. The large spore likewise produces a very small 

 growth, which in this case, however, protrudes a little from 

 the ruptured spore-wall. Upon this several archegones de- 



