2. Proserpinaca. Flowers perfect, the parts in threes. Petals none. Leaves alternate, the immersed pinnately dissected.
3. Hippuris. Flowers usually perfect. Petals none. Stamen, style, and cell of the ovary only one. Leaves entire, in whorls.
4. Callitriche. Flowers monœcious. Calyx and petals none. Stamen 1. Ovary 4-celled, with 2 filiform styles. Leaves entire, opposite.
1. MYRIOPHÝLLUM, Vaill. Water-Milfoil.
Flowers monœcious or polygamous. Calyx of the sterile flowers 4-parted, of the fertile 4-toothed. Petals 4, or none. Stamens 4–8. Fruit nut-like, 4-celled, deeply 4-lobed; stigmas 4, recurved.—Perennial aquatics. Leaves crowded, often whorled; those under water pinnately parted into capillary divisions. Flowers sessile in the axils of the upper leaves, usually above water in summer; the uppermost staminate. (Name from μυρίος, a thousand, and φύλλον, a leaf, i.e., Milfoil.)
[*] Stamens 8; petals deciduous; carpels even; leaves whorled in threes or fours.
1. M. spicàtum, L. Leaves all pinnately parted and capillary, except the floral ones or bracts; these ovate, entire or toothed, and chiefly shorter than the flowers, which thus form an interrupted spike.—Deep water, Newf. to N. Eng. and N. Y., west to Minn., Ark., and the Pacific. (Eu.)
2. M. verticillàtum, L. Floral leaves much longer than the flowers, pectinate-pinnatifid; otherwise nearly as n. 1.—Ponds, etc., common. (Eu.)
[*][*] Stamens 4; petals rather persistent; carpels 1–2-ridged and roughened on the back; leaves whorled in fours and fives, the lower with capillary divisions.
3. M. heterophýllum, Michx. Stem stout; floral leaves ovate and lanceolate, thick, crowded, sharply serrate, the lowest pinnatifid; fruit obscurely roughened.—Lakes and rivers, Ont. and N. Y. to Fla., west to Minn. and Tex.