Rhodora. 
JOURNAL OF 
THE NEW ENGLAND BOTANICAL CLUB 
Vol. 22. February, 1920. No. 254. 
THE GENUS ELODEA IN NEW ENGLAND. 
Hanorp Sr. JOHN. 
Many New England botanists have recently realized that Elodea, 
as represented in their region, was not one uniform species, E. cana- 
densis Michx, as it had so long been considered. The credit for this 
renewal of interest in the genus should, in large part, go to Dr. P. A. 
Rydberg, who perceived the fundamental importance of the floral 
differences, correlated them with the leaf characters, and gave us our 
first comprehensive treatment’ that even approximated the true 
taxonomic relationships. 
Adherents of the International Rules, however, cannot follow 
Rydberg in adopting Rafinesque's name Philotria,? since Elodea of 
Michaux is the first published name for the genus. The earlier name 
Elodes of Adanson? for what is now considered a section of Hypericum, 
would not under the International Rules invalidate Elodea of Michaux, 
even if the former were still maintained as of generic rank. 
The reason for the imperfect understanding of this genus is, of 
course, the fact that the best characters are to be found in the flowers, 
which are so evanescent that they may be found on only a few days 
out of the year. Sterile material can be identified with reasonable 
surety, but only after one has determined the specific limits by the 
study of flowering material. 
Michaux when founding the genus described! his Elodea canadensis 
as with perfect flowers, having the floral tube prolonged into a long 
1 Rydberg, P. A., Notes on Philotria Raf. Bull. Torr. Bot. Cl. xxxv. 457—065 (1908). 
2 Rafinesque, C. S., Review of Pursh’s Flora of North America. Am. Monthly 
Mag. ii. 175 (1818). 
3 Adanson, M., Fam. des PI. ii. 444 (1763). 
1 Michaux, A.. Fl. Bor.-Am. i. 20 (1803). 
