11 
In shallow water or mud. The plant was originally collected by 
Humboldt and Bonpland near Bogota in the United States of 
Colombia, but it has since been found in many other parts of 
South America. The writer gathered it at Buenos Aires. It oc- 
curs on Vancouver's Island (Macoun.), in San Bernardino county, 
Cal. (Parish), and Chihuahua, Mexico (Pringle). (Plate XXIV.) 
4. POTAMOGETON, І. Sp. Pl. 126 (1753). 
Leaves alternate or the uppermost opposite, often of two kinds, 
submerged and floating, the submerged linear and grass-like, the 
floating coriaceous, lanceolate, elliptical, ovate or oval. Spathes 
stipular, often ligulate, free or connate with the base of the leaf or 
the petiole, enclosing the young buds and usually soon perishing 
after expanding. Peduncles axillary, usually emersed. Flowers 
small, spicate, greenish or rufescent. Perianth segments 4, shortly 
unguiculate, concave, valvate in aestivation. Stamens of 4 sessile 
anthers, inserted on the claws of the sepals. Ovaries 4, sessile, 
distinct, 1-celled, 1-ovuled, attenuated into a short, erect ог re- 
curved style, or with a sessile stigma. Fruit of 4 ovoid or subglo- 
bose drupelets, the pericarp usually thin and hard or spongy. 
Seeds crustaceous, exalbuminous, campylotropous, with an unci- 
nate embryo the radicular end of which is thickened. Very fre- 
quently amphibious forms of many of the floating-leaved species 
occur, which it is difficult to distinguish. These are dwarf, stocky 
forms, generally without submerged leaves, nearly always without 
fruit, and caused by the drying up of the water in which they 
grow. About the only method of deciding the species in such 
cases is by the occurrence of the normal form in the adjoining 
waters, and by the coriaceous leaves and stipules which usually 
retain their normal character. P. pulcher, P. lonchites, P. hetero- 
phyllus and Р. spathuleformis (in England) are greatly addicted 
to this habit. 
By nutlet in the following descriptions is meant the crustace- 
ous seed freed from the pericarp. 
About 65 fairly well-defined species occur in the cool waters of 
the temperate zones in all the continents, and the great bulk of 
them in northern North America, Europe and Asia. Of the 37 
North American species, 14, so far as known, are confined to this 
country. 
