188 



ELEMENTS OP STRUCTURAL BOTANY. 



Fig. 236. 



')'>!. The curious elaters (Fig. 236) attached to the 

 spores doubtless assist them to escape from 

 the spore-cases, and subsequently aid in 

 dispersing them. 



332. The Club-Mosses. Fig. 237 is 



a representation of a branch 

 of Lycopodium clamtum, one of our com- 

 mon Club-Mosses. The creeping stem lies 

 flat upon the ground, and often attains a 

 great length, sending up at intervals erect 

 branches with crowded linear-awl-shaped 

 leaves, some of which, like the one shown 

 in the figure, are terminated by a slender 

 peduncle bearing one or more cylindrical 

 spikes. These are the fertile branches, 

 and the leaves upon them, or at all events 

 upon the slender upper part, are Y<TV much 

 smaller than upon the ordinary sterile 

 branches. 



It is to be observed that the stems and 

 roots of these plants branch diclwiomously 

 (145,. 



333. The sporangia are produced in the 

 axils of the leaves of the terminal spike. 

 One of these leaves, greatly magnified, 

 with its attached sporangium, is shown in 

 Fig. 238. The sporangium opens by a 

 slit at the top to discharge the spores. 



334. It is only quite recently that the, 

 prothallium has been detected. It is 



the case observed as a "yellowish-white 



Fig. 237. 



described in 



Fitf. 236. Spore of Equisetum with eluters ; hijfhh 



Fig. 237. Branch of Lycopodium davatum; natural size. (Thom.) 



