2l8 



BOTANICAL GAZETTE 



[SEPTEMBER 



cortical cylinder will appear, is purely cortical. No differentiation 

 is evident between stelar pericycle and cortex; there is even no 

 endodermis, and therefore there is no ground here for believing 

 that the supernumerary cylinders originate in the pericycle. In 



view of Sister Helen 

 Angela's 9 work with 

 Ceratozamia, in which she 

 found unquestionable 

 cambiums at any place in 

 the cortex from the stele 

 to the periphery, it would 

 be possible for the super- 

 numerary cylinders of 

 Cycas to originate in the 

 cortex. In view of the 

 evidence of fig. 8 it would 

 also seem probable that 

 the cylinders are truly 

 cortical and not stelar. 



There is no evidence 

 of protophloem in con- 

 nection with the cortical 

 cylinder. A transverse 

 section (fig. n), which is 

 thoroughly representative 

 of the state of affairs, 

 shows that practically all 

 cells of the phloem are 

 suberized bast fibers. 

 This, together with the 

 very apparent alignment 

 of the fibers, is convincing proof that no protophloem is present. 



Sections of the first cortical cylinder near the stem base reveal 

 conditions almost identical with those of the normal cylinder, 

 excepting that in the former both protoxylem arid protophloem 



» Dorety, Helen A., The extrafascicular cambium of Ceratozamia. Bot. Gaz. 

 47:150-152. pi. 7. 1909. 



Fig. 9. — Cycas media: transverse section of stem, 

 showing centripetal end of second cylinder; c, 

 cortical cells; x, distinctly pitted xylem cells at 

 tip of bundle; X850. 



