14 
slightest sign of a lamina. I notice that they generally form a 
coriaceous blade at their tips when they reach the surface, show- 
ing that they are true petioles. Being attached to the lower part 
of the stem, they often become extremely long. I have specimens 
in which they are from 15 to 18 inches in length. Commonly 
they perish early, and are seldom seen at the fruiting period. 
Stipules long and acute (sometimes 4 inches), 2-keeled. Pedun- 
cles equalling the stem in thickness, and from 2 to 4 inches in 
length. Spikes cylindrical, sometimes upwards of 2 inches long, 
densely flowered and fruited. Fruit turgid, 2-2 ¥% lines long 
and about 11 lines broad, scarcely keeled, narrowly obovate, 
slightly curved on the face; style short and facial; nutlet hard, 
more or less deeply pitted or impressed on the sides, with 2 grooves 
on the back; embryo forming an incomplete circle, the apex 
. pointing towards the base. 
The floating leaves of this species are occasionally very obtuse 
or acute at the apex and sloping at the base. The Atlantic coast 
forms generally have small coriaceous leaves, while those of Europe 
and our interior states are large. Very rarely floating leaves oc- 
cur with as many as 40 nerves. The stipules also are sometimes 
obtuse and usually deciduous beneath the water. An extreme 
form (var. prolixus, Koch.), growing in deep water and strong cur- 
rents, has all the parts very slender and greatly elongated. Ihave 
collected this with stems 12 feet in length, submerged leaves 21: 
inches long, and floating leaves lanceolate or lance-oblong and 
very acute. 
Common in ponds and streams throughout Canada and 
the United States, extending into Mexico. Equally common 
in Europe. Occurs also in Africa and Asia. Fruits in July and 
August in our Northern States. (Plate XXV.) 
2. POTAMOGETON OAKESIANUS, Robbins, in A. Gray, Man. ed. E 
485 (1867). ; 
Stems very slender, often much branched from below. Float- 
ing leaves elliptical, obtuse at the apex and rounded or slightly 
sub-cordate at the base, 1-2 inches long and 5-9 lines wide, with 
from 12 to 20 nerves and slender petioles 2-6 inches long. Sub- 
merged leaves mere capillary phyllodia, often continuing through 
