74 



BOTANICAL GAZETTE 



[JULY 



— -. > 



Fig. 17 .—L. Phlegmaria: photographs of the clay models of the stele; the ridges 



protoxyl 



traces are represented by projections; px, protoxylem; I, leaf trace. 



A 



Fig. 18. L. Billardieri: transverse section of the strobilus apex, showing the 

 radial organization of the stele; protoxylem groups alternating with phloem; the 

 center of the stele is occupied by the unlignified potential metaxylem cells; px, pro- 

 toxylem; p, phloem; X500. 



