thanks to the various individuals and herbaria for their 
generous assistance and codperation in the course of this 
work. I am indebted to my wife, Dr. Helen B. Correll, 
for her assistance in the final preparation of the manu- 
script. I wish to acknowledge the Research Grant of 
1936 by the American Association for the Advancement 
of Science which was awarded me through the North 
Carolina Academy of Science. 
[ 85 ] 
