THE EQUISETACE/E. 13 



these, upon developing, become either secondary root- 

 stocks pushing up toward the surface, or possibly aerial 

 stems rising above it. From the base of these buds slen- 

 der roots are produced. The sections of the 

 rootstocks are covered with a tawny or blackish 

 felt, which, like the root-hairs, doubtless assists 

 in the work of food-absorption. The buds on 

 the stems readily produce roots if covered with 

 moist earth, while rootstocks exposed to the air 

 soon produce stems. Since the plants are liable 

 to be either covered with mud or washed from 

 their places during freshets, it is a wise provi- 

 sion of Nature that stem and rootstock are, so 

 nearly interchangeable. In certain species the 

 rootstock occasionally develops small round 

 tubers. These resemble the rootstock in struc- 

 ture and may be assumed to be undeveloped 

 branches of it. Their use is unknown, unless 

 they may serve as a storehouse for surplus plant- 

 food. Under certain circumstances they may 

 possibly give rise to new plants. 



r_ , r 1 A Joint of 



1 he spores are always borne at the tips or the the stem. 

 stems in cone-like spikes or catkins. These 



spikes consist of numerous, usually 

 six-angled, plates attached to the stem 

 by a central stalk, and bearing from 

 five to nine little sacs or spore-cases 

 on their margins. The sacs extend 

 SPORE-CASES. horizontally toward the centre of the 

 cone, and only the angular plates to which they are 

 attached are to be seen before maturity. When ripe the 

 cone lengthens slightly, drawing the plates apart, the 

 spore-cases open on the side next the stalk that bears 

 them and the spores escape. 



