210 



CRYPTOGAMS 





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rangia, all of one sort, are borne in leaf axils (s, Fig. 357). 

 The sporangial leaves are usually grouped apart in a " fruit- 

 ing " sj)ike. Spores are of one 

 kind, and give rise to prothallia 

 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), 

 grows preferably in 

 ^4 ij^^ sandy soil, and often 



in moist situations. 

 One of the common- 

 est species is to be 

 found along railroad 

 banks.* The north- 

 ern species are, in 

 general, a foot or so 

 tall, though in the 

 tropics Equisetum 

 giganteum^ a slen- 

 der, clambering species, reaches a heiglit 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 they spring 

 from the nodes and display the same arrangement of 

 reduced foliage (Fig. 358). 



492. The terminal portion of fertile shoots is converted 

 into a spore-bearing region (/), in which the leaves are 

 peculiarly modified (Fig. 358, B^ C). They are peltate in 

 form, and bear on the under (or inner) side pocketlike 

 sporangia projecting toward the stem. The spores are 

 very numerous. Each one is provided with two narrow 

 strips of membrane (called elaters. Fig. 358, i>), fastened 

 to the spore at their middle points, the four extremities 



357. Lycopodium: /, fruiting ponion; s, spo- 

 rangium in axil of a sporopliyll. 



