88 
middle one often slightly toothed ог undulate and with a projec- 
tion at the base; ‘face arched, beaked with a short, recurved style; 
embryo slightly incurved. 
The propagating buds of this species are very unlike those of 
No. 20, consisting only of the ordinary terminal leaf bud which 
drops off near the end of the branch, sinks to the bottom and rests 
in the mud during the winter. It is, however, a very common 
source of propagation. 
An elegant plant, with bright smooth leaves in fascicles at the 
summits of the branches. It may be distinguished from other 
North American species, and from Heteranthera graminea with 
flowerless forms of which it is sometimes confounded, by the nu- 
merous fine nerves on the leaves. 
In still or slowly moving water in Northern regions. New 
Brunswick to the Saskatchewan, Canada (Macoun); Vermont to 
New Jersey and westward to Iowa, Lake Superior and Oregon 
(Hall, No. 491, fide Brew. and Wats. Bot. Cal... Common in 
Europe. July, August. (Plate XLV.) 
22. POTAMOGETON Нили, Morong, Bot. Gaz. vi. p. 290 (1881). 
Stems slightly compressed, slender, widely branching, 1-2 feet 
in height. Leaves linear, acute or abruptly acute and cuspidate, 
often almost aristate, 1—21% inches long and 15-114 lines wide, 3- 
nerved, the lateral nerves delicate and nearer the margins than the 
midrib, the midrib below often compound. Stipules whitish, 
many-nerved, obtuse, 3-5 lines in length. Peduncles about half 
an inch long, erect or slightly recurved, more or less clavate. 
Spikes capitate, 3-6 fruited. Fruit obliquely obovate, obtuse at 
the base, 134-2 lines long by 1-11 lines broad, tricarinate on the 
back, the middle keel sharp and more or less undulate, flat on the 
sides, the face slightly arched; style nearly facial, short, recurved; 
embryo apex pointing transversely inwards. 
There are two forms of this species, the one biglandular at the 
base of the leaves, and the other glandless. I found it growing in 
the small pot ponds of Manistee, Mich., each pond having its own 
form and apparently never mixing. In general appearance similar 
to the large forms of P. foliosus, but allied by its peduncles, spikes 
and fruit to P. obtusifolius and Р. zosterefolius, and still more 
