46 THE AMERICAN MIDLAND NATURALIST 
“small,” and leaves ‘‘obtuse” or “acute” constitute some of 
the most important characters of distinction, yet with a geo- 
graphic distribution of so marked characteristic, that their _ 
validity as species appears indisputable. 
Figure 5. Leaf of a mature specimen of the variety pusilla; natural 
size. % 
Regarding Arisaema triphyllum we have a clear case in 
which “seasonal dimorphism” has produced a type, which 1 
believe is about to develop as a distinct species. And there 
