CYCADOFILICALES 7 



tostelic stem, which merges directly into a siphonostelic condition 

 with internal phloem; while in Osmunda, although there is usually 

 in the adult stem a siphonostele without internal phloem, in O. 

 cinnamomea (27, 31) occasionally internal phloem is found. Neither 

 type of siphonostele is .extensively displayed among ferns (36), the 



Fig. 4. — Osmunda cinnamomea: transverse section of stem, showing the ectophloic 

 siphonostele; X25. — After CoOT,TER (88). 



amphiphloic type occurring, for example, in Adiantum, Matonia, 

 Loxsoma, Aneimia mexicana, etc., and the ectophloic type in Osmunda 

 (fig. 4), Platyzoma,^ Schizaea, etc. 



The prevailing type of stele among the ordinary ferns is the poly- 

 stelic (10), occurring in most Polypodiaceae, Dicksoniaceae, Cyathe- 

 aceae, Marattiaceae, etc. (36). The type is well illustrated by Pteris 



1 A monotypic genus regarded by some taxonomists as a species of Gleickenia. 



