30 
This species seems to be intermediate between 2. heterophyllus 
and P. ducens. It may generally be distinguished from the former 
by its larger size, by floating leaves of thinner texture and more 
sloping at the base, by its larger, more sharply pointed and 
strongly undulate submerged leaves and larger fruit. From 2. 
lucens it may be distinguished by its floating leaves, which are 
lacking in Р. /ucens, as well as by its smaller fruit and other char- 
acteristics. It usually sends up coriaceous floating leaves late in 
the season. It flowers freely, but seldom fruits in the United 
States. It commonly occurs in rather shallow and quiet waters, 
but is not widely diffused. 
A form collected by Prof. Macoun in Methy Lake, Lat. E Hu 
Canada, and which I have not seen, is thus named and described 
by Mr. Bennett in Jour. Bot. for May, 1891, p. 151. 
“ Var. Methyensis. Differs from any form of the type in America 
or Europe by the long, narrow middle leaves. The upper leaves 
are oval, semi-coriaceous, with long stipules, combining the habit 
of longifolius, Gay. and the /ucens No. 607 of Herb. Fl. Ingrice; 
fruit smaller, and the embryo more curved.” 
The type has been found in Canada in the Provinces of Ontario 
and Quebec (Macoun); Fresh Pond, Cambridge, Mass. (Morong); 
Wenham, Mass. (Faxon, Morong); Pine Plains, N. Y. (Hoysradt); 
Lake Cayuga, N. Y. (Dudley); Oneida and Seneca Lake, N. Y. 
(Morong); Delaware river, above Phillipsburg, N. J. (Porter); 
Pine Station, Ill. (Hill); Frankfort, Mich. (Hill); Lewis Lake, 
Wyoming (Clifford Richardson); Montana (Hayden Survey); 
Florida (Curtiss); Texas (Reverchon, Wright). Common in Eng- 
land and Continental Europe. (Plate XXXVII.) 
14. POTAMOGETON LUCENS, L. Sp. Pl. 126 (1753). : 
Stem thick, branching below and often with masses of short 
leafy branches at the summit. Destitute of propagating buds or 
glands. Leaves all submerged, elliptical or lanceolate, uppermost 
often oval, rounded at both ends and merely mucronate, usually 
acute or acuminate and cuspidate, sessile or short petioled, 214-8 
inches long and 8-20 lines wide. The nerves are commonly 13, but 
sometimes fewer, and the tips frequently serrulate. They are 
rarely shining, though the name would imply otherwise. Stipules 
1-3 inches long, obtuse, bicarinate, commonly loose and spread- 
