XI 



LEPTOSPORANGIATAl HETEROSPOREJE 



441 



seem to be with the Osmundacere, luit in the structure and ar- 

 rangement of their vascular Ijundles they are more Hke tlie 

 Gleicheniace?e. 



Of the two famihes of the Hydropterides, the Salviniace^e 

 shows several points of resemblance to the Hymenophyllacea^. 

 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 



Sfflvinia 



AzollOt 



Eusporan^iattr 



roots in Salvinia is suggestive also of the similar absence in 

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

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

 phyllacese examined, which all possess the pyramidal initial, 

 but possibly further examination may show forms with an 

 initial cell similar to that of Azolla or Salvuiia. 



The Marsiliaceas, except for their marked heterospory, are 

 typical leptosporangiate forms. The writer has been inclined 

 to assign them a position near the Polypodiaceae, but recent 



