Howe : Riccia Beyrichiana and Riccia dictyospora 165 



other important characters which distinguish the spores of Riccia 

 Beyrichiana from those of R. dictyospora. Age has not made the 

 mature spores of Riccia Beyrichiana the more angular, it has not 

 increased their size, it has not left more or less of a wing at their 

 angles, it has not smoothed off their inner faces, and it has not 

 doubled the diameter of the meshes of the outer face. 



We 



dictyosp 



Among American species, 



Riccia Americana and R. Austini resemble it in the entire absence 

 of wing-margins to the spores but in other respects have little in 



common with our plant. 



Riccia Beyrichiana apparently remains a species unknown ex- 

 cept from the original collection of August 13, 1833. It is to be 

 hoped that botanists resident in the Southern States and those 

 traveling in that region will consider its rediscovery a problem 

 worthy of their attention. 



Columbia University, ii February, 1901. 



