PTERIDOPHYTA 



301 



The Root 



The roots arise from the lowest nodes of the buds, but do not 

 usually develop except from the buds formed upon the rhizome. 

 The dormant roots of the aerial shoots may, however, be forced into 

 growth under special conditions of light and moisture. 



The origin of the roots and their development follow very closely those of 

 the typical Ferns (Fig. 266). The root-cap is somewhat more massive and the 

 stratification not so evident as in most Ferns. The root-bundle in E. telmateia 

 is triarch or tetrarch, with a single very large vessel occupying the centre. The 



A. 



FIG. 267. Equisetum telmateia. A, young sporophyll with primary sporangial cell, 

 sp (X 260). B, C, sections of young sporangia; the archesporium is shaded. 



endodermis is double, and no pericycle is developed. The secondary roots arise 

 from the inner endodermis, and there is a double row of these corresponding to 

 each xylem-mass. The endodermal cell outside of the root-rudiment also grows 

 and divides for a time, forming a " digestive pouch " enclosing the young root. 



The Sporangium 



The sporangia are borne upon umbrella-shaped sporophylls, which are 

 arranged in close circles, forming a cone at the top of the fertile shoot, and 

 represent as many foliar sheaths. The young sporophyll (Fig. 267) is a nearly 

 hemispherical body, which soon assumes a mushroom form. The sporangia arise 



