XI 



LEPTOSPORANGIATJE HETEROSPORE1E 



44i 



seem to be with the Osmunda.cese, but in the structure and ar- 

 rangement of their vascular bundles they are more like the 

 Gleicheniaceae. 



Of the two families of the Hydropterides, the Salviniacese 

 shows several points of resemblance to the Hymenophyllacese. 

 The development of the leaves is strikingly like those of Hy- 

 menophyllaceae with reniform or palmate leaves, and the struc- 

 ture of the sori almost identical. The absence of secondary 



.Salvinia 



Azoll* 



roots in Salvinia is suggestive also of the similar absence in 

 some species of Trichomanes. The two-sided apical cell of 

 the stem is, however, different from that of the few Hymeno 

 phyllaceae examined, which all possess the pyramidal initial, 

 but possibly further examination may show forms with an 

 initial cell similar to that of Azolla or Salvinia. 



The Marsiliacese, except for their marked heterospory, are 

 typical leptosporangiate forms. The writer has been inclined 

 to assign them a position near the Polypodiaceae, but recent 



