XI 



LEPTOSPORANGIAT^ HETEROSPOREJE 



441 



seem to be with the Osmundacese, but in the structure and ar- 

 rangement of their vascular bundles they are more like the 

 Gleicheniacese. 



Of the two families of the Hydropterides, the Salviniaceae 

 shows several points of resemblance to the Hymenophyllacese. 

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

 menophyllace?e with reniform or palmate leaves, and the struc- 

 ture of the sori almost identical. The absence of secondary 



Salvinia 



Azolln 



Eiispora ngiattP 



roots in Salvinla is suggestive also of the similar absence in 

 some species of TricJioinanes. 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 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 



