248 



THE AMEBIC AN NATURALIST [Vol. XLII 



which I have formulated for my own gui< laiiee— it was a 

 necessity that I should formulate some rule— that species, 

 which are concepts, as I take it, for our convenience in 

 discussing the various questions pertaining to plants, 

 should be distinguished by sufficient morphological char- 

 acters, the distinctions based upon physiological differ- 

 ences having subspecific rank. What constitute suffi- 

 cient morphological characters must be left to the indi- 

 vidual judgment. 



