47 
gemmiparus and major, all together forming a well-marked aggre- 
gate. 
A widely-diffused species, common in Canada from New Bruns- 
wick to British Columbia, New England to Louisiana and Texas, 
west to Oregon and California. San Luis Potosi, Mexico, Schaff- 
ner, No. 533. Europe. Pools and ditches. July, August. 
(Plate LHI.) 
30. POTAMOGETON GEMMIPARUS (Robbins) Morong, Bot. Gaz. v. 
51 (1880). 
P. pusillus L., var.? gemmiparus, Robbins in A. Gray, Man. Ed. 
E 489 (1867). 
Stems filiform, branching, terete, greatly varying in height, 
rising from 5 inches to 4 feet, according to the depth of water in 
which it grows; the internodes below, especially in deep water 
forms, as much as 5 inches inlength. Leaves capillary, sometimes 
not as broad as the stem, often with no perceptible midrib, taper- 
ing to the finest point, 1-3 inches long, biglandular at base; 
stipules 1-і inch in length, acute or obtuse, mostly deciduous. 
Rarely flowering, the spikes interrupted, 3-6-flowered; peduncles 
filiform, sometimes a little thickened, %-2 inches long. Fruit ex- 
ceedingly rare, and in size and shape like that of Р. pusillus, except 
that it is flatter and somewhat impressed on the sides. It is com- 
monly propagated by gemmae, which are abundant. The leaves 
and stems are often alike in thickness, so that the plant seems to 
consist of threads, and this with the long, naked internodes, ren- 
ders its appearance very peculiar. 
A few specimens in fruit were obtained at Amherst, Mass. by 
Prof. H. G. Jesup in 1874, and by him sent to Dr. Robbins, who 
thereupon substituted in his herbarium the name here adopted. It 
was first found by Dr. Robbins in the Blackstone Valley from Wor- 
cester, Mass. to Providence, R. L, and has since been collected by 
myself in the Charles River, at South Natick, Mass. Also by Mr. 
J. F. Collins, in Central Pond, R. I. Pools and slow moving 
streams. August, September. (Plate LIV. The rare fruiting 
form is seen on the right.) 
