42 
are 3-nerved or 5-nerved at the base only. Stipules white, hyaline, 
finely nerved, obtuse or acute, 6-12 lines long. Peduncles 1-1% 
inches long, often thicker than the stem and sometimes thickening 
upwards. Spikes when developed interrupted. Fruit quite simi- 
lar to that of P. pusillus, but I find it always with a recurved style, 
generally with a shallow pit on the sides and with the apex of the 
embryo pointing almost directly towards the basal end. The pro- 
pagating buds are similar to those of P. ри из, but not so 
common. 
This species may generally be distinguished from pusillus in 
its various forms by its larger leaves, larger and more flattened 
stems and its more elongated and less branching habit, but the 
two run together so closely that at times it is difficult to separate 
them. It is considered by some authors as intermediate between 
P. pusillus and Р. obtusifolius, and when not in fruit it may be con- 
founded with the latter, but as a rule the glands are smaller and 
duller in tint than in that, and the leaves shorter. P. obtusifolius, 
too, is much more bushy in habit, sometimes even spreading out 
in fan-shape, and it is extremely rare that its leaves have more 
than 3 nerves. 
The species rare in the United States. New Brunswick, On- 
tario and British Columbia (Macoun); Lake Champlain, Vt. 
(Faxon); Lake Seneca, N. Y., abundant (Morong); Wisconsin 
(Lapham); Michigan (Hill); Minnesota (Cratty). July-Septem- 
ber. (Plate XLIX. A leaf magnified is shown on the left.) 
26. POTAMOGETON RUTILUS, Wolfg. in R. and S. Mant. iii. 362 
1827). ` 
P. cespitosus, Nolte, fide Reich. Ic. vii. 15. 
Stems very slender, 8 to 24 inches in height, compressed; roots 
finely fibrous, sending up many stems, but each stem simple or 
nearly so. I find them occasionally rising from a bit of stem or 
hybernaculum, showing that the species is sometimes, at least, 
propagated in this way, but usually without propagating buds. 
Leaves I to 1% inches long and ¥ to Y a line broad, acute or 
acuminate, strict, nearly erect, 3-5 nerved, revolute, nerves promi- 
nent beneath, the midrib compound, especially at the base, where 
it often divides into 2 and even 4 strongly marked nerves, often 
