— 4 i— 



Asplenium ebeneum Hortoncc. 



Athyrium Filix-focmina forma multifida. 



Athryiwm Filix-focmina forma polycladon. 



Athyrium Filix-foemina forma rhccticum. 



Athyrium Filix-focmina forma angustum. 



Asplenium Trichomanes incisum. 



Dicksonia pilosiuscula forma schizophylla. 



Onoclea sensibilis obtusilobata. 



Struthioptcris Germanica obtusilobata. 



Osmunda Claytoniana dubia. 



Equisetum Huviatile polystachyon. 



Equisetum littorale gracilis. 



Equisetum palustre polystachyum. 



Equisetum palustre ramulosum. 



Ly cop odium complanatum Wibbei. 



This shows a beginning of what might be done if one 

 was inclined to magnify small differences and freak 

 forms. 



A T ew York Botanical Garden. 



WHAT CONSTITUTES A SPECIES IN THE 

 GENUS ISOETES. 



By YVillard N. Clute. 



In selecting the title for this article I had no intention of 

 intimating that anywhere in it will there be found a 

 definition of an Isoetes species; on the contrary, having 

 had occasion recently to work carefully through the Xorth 

 American species, I have been impressed with the fact 

 that no one as yet appears to have a very clear idea of 

 what constitute specific differences. What I may have to 

 say on the subject, therefore, will be largely in the nature 

 of comment and query in the hope that it may induce 

 some older student of the genus to give us a more defi- 

 nite statement of the basis for making Isoetes species than 

 has yet appeared. The marks by which the species are 

 distinguished are so obscure as to be puzzling to all but 

 the select few. and in consequence the species have been 



