ed 
te i ll 
ee a ee a 
GEOGRAPHIC DISTRIBUTION OF ISOETES SAC- 
CHARATA. 
CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY. 
GEORGE HARRISON SHULL. 
(WITH MAP) 
WHILE making a study of the aquatic vegetation of Chesa- 
peake Bay for the U. S. Bureau of Plant Industry during the 
summer of 1902, I located several new stations for Jsoetes sac- 
charata Engelm. This species has had an interesting history, 
and as our knowledge of its range has greatly increased within 
the last few years, I have thought it desirable to publish the 
accompanying map showing the exact distribution as now known, 
to give a detailed account of its history, and to discuss briefly 
several problems which have presented themselves for solution. 
For a quarter of a century Jsoetes saccharata Engelm. was 
known only from its type locality on the Wicomico River and 
from the Nanticoke, which empty into the bay by a common 
mouth opposite and a little north of the mouth of the Potomac. 
Far up the Wicomico, about a mile below the town of Salisbury, 
Maryland, the plant was first discovered by William M. Canby 
in 1863. The material was submitted to Dr. Engelmann, who 
was at that time the highest American authority on the genus, 
and was first described by him in Gray’s Manual, 5th edition, p. 
676, 1867. In 1874 Canby found asecond station at Seaford, 
Del. Not until 1888 was it collected at a third station, when it 
was found by Vasey and Coville near Alexandria, Va., in Hunt- 
ing Creek, a tributary to the Potomac. The material obtained 
here was not recognized for some years as identical with Canby’s 
material, and was referred by Theo. Holm to Jsoetes riparia 
Engelm.? The next year Coville found it at Mount Vernon on 
the Potomac, but this collection seems to have been overlooked 
* Proc. Biol. Soc. Washington 7: 132. 8 Ap 1892. . 
1903] 187 
