PTERIDOPHYTA 



221 



per 



Fig. 176. Cross section of the central portion of the stem of Lycopodium liicidulum, show- 

 ing the "radial" type of stele, X250; end, endodermis; per, pericycle; px, protoxylem; mx, 

 metaxylem; ph, phloem. 



Fig. 177. Cross section of the central portion of the stem of Lycopodium cernuum, showing 

 the "mixed" type of stele, X70. 



