This section is from the book "Sub-Alpine Plants Or Flowers Of The Swiss Woods And Meadows", by H. Stuart Thompson. Also available from Amazon: Sub-Alpine Plants: Or, Flowers of the Swiss Woods and Meadows.
Plants usually growing in water. Leaves sheathing at the base, often floating on water. Flowers green, bisexual or unisexual. Perianths 3-4 lobed or 0. Stamens hypogynous. Ovary of 1-4 carpels. Style I. One seed in each carpel.
Leaves floating and opaque or submerged and translucent, stipulate or not. Perianth-segments 4, small, green. Stamens 4.
A rather large genus spread almost all over the globe; but with only one or two representatives in the high Alps.
Stem branching from the base. Leaves linear-filiform, 1-nerved. Spikes on long stalks. Fruit globular, with very short beak.
Alpine lakes, and rarely lower. It is abundant at the shallower end of the Lake of Mont Cenis (6300 feet) and in several Alpine lakes in Switzerland. It flowers in July; rare.
S. Tyrol, Switzerland, Western Alps, Central and Northern Europe. British.
Stem simple, cylindrical; submerged leaves narrow-lanceolate, sub-obtuse, translucent; floating-leaves, when they exist, coriaceous, oblong-spathulate, reddish. Stipules large. Fruiting-spike 2-4 cm. long, cylindrical, compact, on longish peduncles. Carpel compressed, keeled at the back, with distinct beak.
Stagnant or slowly running water, especially in the mountains.
Europe, N. and N.W. Asia, N. America. British.
Many of the British species of Potamogeton are found in Switzerland, but chiefly in the plains.