45 
nearly touching the point of the base. The plant is scantily fur- 
nished with reproductive buds like those of P. pusillus. Proliferous 
shoots at the summit of the stem and on the upper branches, 
above the floating leaves, appear late in the season just as the 
plants are beginning to decay, a very peculiar habit. 
In slowly-moving water, 3-4 feet deep, in dense masses, 
Charles River, Dedham, Mass. (Faxon, Morong); Salisbury, 
Conn. (Robbins); Hemlock Lake, Livingstone Co. N. Y., and 
Bear Lake, Mich. (Hill). July, August. (Plate LH. Sterile and 
fertile branches.) 
29. POTAMOGETON PUSILLUS, L. Sp. РІ. 127 (1753). 
A variable species with filiform, branching stems from 6 inches 
to 2 feet in height. Leaves all submerged, linear, obtuse and 
mucronate or acute at the apex, I-3-nerved, biglandular at base, 
rarely glandless, 1-3 inches long and Y-% line broad. The typ- 
ical form (var. vulgaris. Fries. Nov. p. 49), has leaves 3-nerved, 
from a little less than % to 34 line broad, obtuse or shortly acute, 
and not unfrequently cellular-reticulate between the midrib and 
the lateral nerves. The leaves are sometimes revolute and slightly 
ridged in the middle, resembling in this respect those of P. rutilus. 
Another common form has the leaves about 1% line wide, almost 
setaceous, 1—3-nerved, the lateral nerves obscure or obsolete, acute 
(var. Zemuissimus, М. and К. Deut. Fl. i. 857. P. gracilis, Fries, 
Nov. p. 50). 
Both of these forms are occasionally provided with reproduc- 
tive buds. 
Stipules short, hyaline, obtuse, when enclosing the bud boat- 
shaped. Peduncles vary greatly in length, generally from 3 to 9 
lines long, but occasionally elongated from 1 to 3 inches, and 
sometimes thickened in fruit. Spikes about as often interrupted 
as capitate in all the forms, 3-10-flowered. Fruit obliquely ellip- 
tical, 34-1 line long and 10-34 line wide, curved and 2-grooved 
on the back, or sometimes with 3 distinct keels; face slightly 
arched or often with a projecting curve above and an inward curve 
below, beaked by a short, straight or recurved style; apex of the 
embryo slightly incurved and pointing obliquely downwards. 
