202 - BOTANICAL GAZETTE [SEPTEMBER 
Isoetes saccharata should prove to be polymorphic, as these facts 
suggest, the result will be of interest in its bearing upon such 
species as J. echinospora Durieu and J. velata A. Br., whose 
numerous intergrading forms have proved so baffling to syste- 
matists. 
By way of summary, then, /soetes saccharata Enge|m. has been 
located in a number of tributaries of Chesapeake Bay from the 
the Potomac and Wicomico Rivers to the head of the bay. 
The species is conceived to be autochthonous in Chesapeake 
Bay, and to bear toward Jsoetes riparia Engelm. the relation of 
parent to offspring. 
Its present distribution is explained by the geomorphic move- 
ments of the coastal plain. 
Certain facts are presented which suggest that the species is 
polymorphic, and that the varieties Palmeri A. A. Eaton and reticu- 
lata A. A. Eaton are untenable. 
I take pleasure in acknowledging my indebtedness to Wm. 
M. Canby, F. V. Coville, T. C. Palmer, E. S. Steele, and W. R. 
Maxon for notes on their several collections of /soetes saccharata 
Engelm. and its forms; to Dr. J. N. Rose for data from U. S. 
National Herbarium, and Dr. Wm. Trelease for data from the 
Herbarium of the Missouri Botanical Gardens, and from G. 
Engelmann’s manuscript notes; also to Miss Veva M. Brower for 
notes on the Nanticoke River at Seaford, Del. But I am under 
special obligations to A. A. Eaton, who has kindly examined all 
my material and has encouraged me with suggestions and criti- 
cisms on the discussions involved in this paper. To all of these 
I wish to express my sincere thanks. 
THE UNIVERSITY OF CHICAGO. 
