MEMOIRS 
OF THE 
Vol. Ш. No. 2. 
The Naiadacez of North America. 
By THOMAS Мококс. 
(PLATES XX.—LXXIV.) 
The first botanist to reduce the North American species of 
Potamogeton to anything like a complete and intelligible sys- 
tematic shape was Dr. J. W. Robbins, of Uxbridge, Mass. To 
his pen is due the description in Gray's Manual, edition 5, of the 
species within the range of that work. To this he added in the 
Botany of King's Expedition an account of the species found in 
Nevada, Utah and the adjoining regions, completing his work in 
the Botany of California by Brewer and Watson by a determina- 
tion of the species on the Pacific coast which were then known. 
At his death, in 1875, Dr. Robbins bequeathed to me his collec- 
tions, containing not only the gatherings of many years by his 
own hand, but also specimens from the Herbarium of Tuckerman, 
one of the earliest students of this genus, and from Oakes, his 
close friend and collaborator, in whose lamented early death our 
country lost one of its most promising naturalists. Dr. Robbins 
left with his Herbarium an injunction that his plants should be dis- 
tributed as widely as possible. I feel, therefore, that I am execu- 
ting a sacred trust in issuing a monograph upon the Order that 
includes as its principal part the family upon which my friend ex- 
pended so much thought. Besides this, the paper here presented 
includes not only the embodiment of my friend's most cherished 
convictions, but the results of my own studies in a personal ex- 
ploration of nearly all the waters from Quebec to Virginia, and 
from the Atlantic to the Mississippi. This monograph, however, 
