292 



PEACTICAL BOTANY 



usually unbranehed stems. The small leaves form a sheath 

 about the joints of | the stem (Fig. 244, A, B'). Most of the 



chlorophyll is borne in the 

 stem, and little or no chloro- 

 phyll work is done by the 

 leaves. The commonest f orin 

 now living is known as the 

 Equisetum arvense. 



268. Equisetum arvense: di- 

 vision of labor. The under- 

 ground rootstock is, in early 

 spring, stored with starchy 

 food that was made by the 

 plant during the preceding 

 growing season. Very early 

 in the spring, sometimes be- 

 fore the last snows are gone, 

 there grows up from the root- 

 stock one sporophyll branch 

 (Fig. 244, A). This has no 

 chlorophyll, and at the tip 

 bears the sporophylls in a 

 single dense spike known as 

 a cone or strobilus. Soon there 

 appears from the rootstock 

 another branch which 

 bears chlorophyll. The 

 sporophyll branch soon 

 dies, but the chloro- 

 phyll branch subdivides 

 extensively, producing 

 a heavy, bushy plant, 

 —the "horsetail" (Fig. 

 244, £}. This grows 

 throughout the season 

 and manufactures food, 



Fig. 244. Equisetum arvense 



A, a plant in early spring condition ; r.s, rhizome ; 

 s.ti, spore-bearing branch, with the collection of 

 sporophylls (strobilus or cone) at its tip; f.h, 

 foliage branch, which later expands as in B; 

 0, one sporophyll from the cone, showing the stalk 

 (st) and several sporangia (sp). D and E, spore with 

 elaters. A and B one half natural size, Cmagnified 

 about twenty times, and D and E greatly enlarged 



