210 



CHyPTOGAMS 



raiiq-ia, all of one sort, are borne in leaf axils (s, Fig-. 357\ 

 The sporangia! leaves are usually grouped apart in a " fruit- 

 ing " spike. Spores are of one 

 kind, and give rise to protliallia 

 which in many species are fleshy, 

 tuberculate bodies, leading a more 

 or less subterranean existence. 

 Fertilization and the growth of 

 the sporophyte have much the 

 same history as in Ferns. 



490. Equisetum, the Horsetail, 

 or Scouring Rush (Fig. 358), 

 A grows preferaljly in 



' "V sandy soil, and often 



in moist situations. 

 One of the commnn- 

 est species is to be 

 found along railroad 

 banks. Tlie north- 

 ern species are, in 

 general, a foot or so 

 tall, tljougli ill the 

 tropics Equiisctuiii 

 giganteum, a slen- 

 der, clamljering sjiecies, reaches a height of thirty feet. 



491. The upright shoots spring from a running base. 

 The stem is clothed at the nodes by short sheaths of con- 

 joined scaly leaves. When branches arise thej^ spring 

 from the nodes and dis[)lay the same arrangement of 

 reduced foliage (Fig. ooS). 



492. 'J'lic terminal pdi-tion of fertile shoots is converted 

 into a spore-ljearing region (f). in which tlie leaves are 

 peculiarly moditied (Fig. -"-IS. B. (.'). Tliey are peltate in 

 form, and liear on llie under (or inner) side [locketlike 

 ispoiunif/ia projecting toward tlie stem. Tlie spores are 

 \-ery nunim-iius. l^aeh (uie is provided witli two narrow 

 strips of nienil)rane (calleil elaters. Fig. 3.58. I)'), fastened 

 to the spore at their middle points, the four extremities 



357. Lycopodium: /, fruitmg ixiriioij; 

 rangium in axil oi a spurupliyii 



spo- 



