170 Rhodora [SEPTEMBER 
NOTES UPON THE ABOVE LIST. 
Potamogeton confervoides Reichenb. ‘This species (as P. Tucker- 
mani Robbins) is listed without station in J. L. Bennett's Plants of 
Rhode Island. There is no specimen in Mr. Bennett's herbarium, 
and the occurrence of this unique species chiefly in subalpine or very 
cold ponds indicates that its Rhode Island record is extremely doubt- | 
ful. 
P. perfoliatus L., although reported from all the New England states, 
has been examined only from Maine. All the material from the other 
New England states seen by the writer has been either P. bupleuroides 
Fernald or P. Richardsonii (Benn.) Rydb. 
Many minor hybrids are recognized by Old World students of Po- 
tamogeton. Little has been done in America to make out our hybrid 
forms and most such plants are at present omitted from the list. 
SUGGESTIONS FOR SPECIAL OBSERVATION. 
Najas flexilis (Willd.) Rostk. & Schmidt, var. robusta Morong. 
This extreme form is known in New England only from ponds of east- 
em Massachusetts. It is found, however, in New York and should 
be sought in Rhode Island and Connecticut. 
Najas quadalupensis (Spreng.) Morong, quickly distinguished from 
N. flexilis by its dull conspicuously reticulated seed, extends north- 
ward from Tropical America to eastern Pennsylvania, and has recently 
been reported from southern; New York. Itis to be expected in south- 
eastern Massachusetts and Rhode Island. 
Potamogeton angustifolius Berchtold & Presl, var. connecticutensis 
(Robbins) Benn. (P. lucens, var. connecticutensis Robbins) has the 
3-keeled fruit of P. angustifolius but differs in its greater size, its fruits 
being 4-4.5 mm. long, while those of P. angustifolius are 3-4 mm. 
long. "Тһе variety is known in Vermont and Connecticut, and should 
be sought in central and western Massachusetts. 
P. epihydrus Raf., var. cayugensis (Wiegand) Benn. (P. Nuttalii, 
var. cayugensis Wiegand) occurs in eastern Maine, in Connecticut, 
and in Lake Memphremagog, Quebec, and is to be sought in lakes 
of New Hampshire, Vermont, and western Massachusetts. It differs 
from the common P. epihydrus (P. pensylvanicus Willd., P. Nuttalit 
