332 



LYCOPODIALES 



derivative. Of the former S. spmnlosa, A. Br., 'is the best known, and it 

 will be seen that its vascular anatomy, which differs from that of all 

 other Selagincllas, shows points of interesting comparison on the one 

 hand with Lycopodium, and on the other with the dendroid Club-Mosses. 

 The hypocotyl, and the lower parts of the axis, with its branches, are 

 traversed by a cylindrical stele, which is peculiar in having a central 



A 



H.G. 



F.E. 



FIG. 



173. 



Selaginella spinulosa. A. Transverse section of the trailing stem showing central 

 protoxylem. # = pericycle ; <5 = protophloem ; c = phloem parenchyma ; rf=metaxylem. 



X275- B = transverse section of upper part of axis, showing seven protoxylems. .X35o. 



C-G scheme of arrangement of the protoxylems in sections taken successively from 

 below upwards. (After Harvey-Gibson.) 



strand of protoxylem surrounded by metaxylem : this is further invested 

 by a narrow band of phloem surrounded peripherally by a sheath 

 resembling a pericycle, and by the trabecular endodermis so characteristic 

 of Selaginella (Fig. 173): according to Strasburger both of the latter 

 layers are derived from the cortex, as they are also in Lycopodium. 1 

 In passing upwards in the strobilus the stele loses its peculiarity of 

 having a central protoxylem : for the strand divides, and the branches 

 diverge outwards to the periphery of the wood, where they appear in 



1 Leitungsbahnen, p. 458. 



