XX] 



MARATTIALES 



319 



tracheae are added to the primary xylem by the activity of the adjacent 

 parenchyma. The vascular bundles in the petiole form more or less regular 

 concentric series ; they have no endodermis and are characterised also by 

 the large size of the sieve-tubes (st, fig. 243). 



The roots of Marattiaceous ferns (fig. 244) are characterised by the 



Fig. 243. Angiopteris evecta. Section of petiole (considerably reduced) and of 

 a single vascular bundle (magnified) : px, protoxylem ; st, sieve- 

 tubes. 



FiQ. 244. Angiopteris evecta. Transverse section of root, ■with part of the 

 stele magnified: s, sieve-tubes; p, phloem; px, protoxylem. 



larger number of xylem and phloem groups ; the stele is polyarch and not 

 diarch, tetrach or hexarch as in most Leptosporangiate ferns. 



Archangiopteris. This monotypic genus, discovered by Mr Henry in 



South Eastern Yunnan, was described by Christ and Giesenhagen in 



18991. The comparatively .slender rhizome has a fairly simple vascular 



system^. The simply-pinnate leaves bear pinnules like those of Danaea, 



1 Christ and Geisenhagen (99). ^ Gvfynne-Vaughau (05). 



