ELEMENTS OP STRUCTURAL BOTANY. 



Fig. 236. 



331. 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 clavatum, 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 very much 

 smaller than upon the ordinary sterile 

 branches. 



It is to be observed that the stems and 

 ro^>ts of these plants branch diclioiomously 

 (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 



described in the case observed as a " yellowish- white 



Fig. 236. Spore of Equisetum with elaters ; highly magnified. 



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



