REYISIOH 
North American Umbelliferse. 
[Issued December, 1888.] 
The Order LhnbelUferce has always been considered a most 
perplexing one, chiefly because the characters ordinarily used 
among flowering plants are of no avail, and the attempt to use 
them has led to confusion. The order must still be considered a 
difficult one to the ordinary student, inasmuch as it demands care- 
ful sections of the fruit and an examination of rather minute struct- 
ures. 
In our revision of the North American species we are much 
indebted to the hearty co-operation of botanists and desire to make 
the following acknowledgements: To our lamented leader, Dr. 
Asa Gray, the inception of the work was due, and his constant 
encouragement at first made the final loss of it doubly felt. Dr. 
Sereno Watson has given every assistance that his great knowl- 
edge of the order could suggest, besides placing the rich collect- 
ions of Harvard Univei'sity at our disposal; and it is but justice to 
say that the work would have been well nigh impossible had it 
not been for his masterly Bibliographical Index. Dr. N. L. Brit- 
ton has also enabled us to study the valuable collections of Colum- 
bia College, especially desirable on account of its Torrey collec- 
tion. The Philadelphia Academy also generously submitted their 
collection of Umbellifers to our inspection, a very important aid 
on account of the number of Nuttallian types it contains. The 
herbarium of the Agricultural Department was also placed at our 
