Flowers perfect. Calyx-tube 3-sided, the limb 3-parted. Petals none. Stamens 3. Stigmas 3, cylindrical. Fruit bony, 3-angled, 3-celled, 3-seeded, nut-like.--Low, perennial herbs, with the stems creeping at base, alternate leaves, and small flowers sessile in the axils, solitary or 3--4 together, in summer. (Name applied by Pliny to a Polygonum, meaning _pertaining to Proserpine_.) 1. P. palústris, L. _Leaves lanceolate, sharply serrate_, the lower pectinate when under water; fruit sharply angled.--Wet swamps, N. Eng. to Fla., west to Minn. and Tex. 2. P. pectinàcea, Lam. _Leaves all pectinate_, the divisions linear-awl-shaped; fruit rather obtusely angled.--Sandy swamps, near the coast, Mass. to Fla. and La. 3. HIPPÙRIS, L. MARE'S TAIL. Flowers perfect or polygamous. Calyx entire. Petals none. Stamen one, inserted on the edge of the calyx. Style single, thread-shaped, stigmatic down one side, received in the groove between the lobes of the large anther. Fruit nut-like, 1-celled, 1-seeded.--Perennial aquatics, with simple entire leaves in whorls, and minute flowers sessile in the axils in summer. (Name from ἵππος _a horse_, and οὐρά, _a tail_.) 1. H. vulgàris, L. Stems simple (1--2° high); leaves in whorls of 8 or 12, linear, acute; fruit nearly 1´´ long.--Ponds and springs, Penn. to Ind. and Minn., and northward. (Eu.) 4. CALLÍTRICHE, L. WATER-STARWORT. Flowers monœcious, solitary or 2 or 3 together in the axil of the same leaf, wholly naked or between a pair of membranaceous bracts. Sterile flower a single stamen; filament bearing a heart-shaped 4-celled anther, which by confluence becomes 1-celled, and opens by a single slit. Fertile flower a single 4-celled ovary, either sessile or pedicelled, bearing 2 distinct and filiform sessile, usually persistent stigmas. Fruit nut-like, compressed, 4-lobed, 4-celled, separating at maturity into as many closed 1-seeded portions. Seed pendulous, filling the cell; embryo slender, straight or slightly curved, nearly the length of the oily albumen.--Low, slender and usually tufted, glabrous, or beset with minute (microscopic) stellate scales, with spatulate or linear entire leaves, both forms of leaves often occurring on the same stem. (Name from καλός, _beautiful_, and θρίξ, _hair_, from the often almost capillary stems.) [*] _Small annuals, forming tufts on moist soil, destitute of stellate scales; leaves uniform, very small, obovate or oblanceolate, 3-nerved, crowded; bracts none._ 1. C. defléxa, Braun. var. Austìni, Hegelm. Stems ½--1´ high; fruit small ({1/3}´´ broad), broader than high, deeply notched above and below, on a pedicel often nearly of its own length or nearly sessile; lobes of the fruit narrowly winged and with a deep groove between them; persistent stigmas shorter than the fruit, spreading or reflexed; leaves 1--2´´ long. (C. Austini, _Engelm_)--On damp soil, N. Y. and N. J. to Ill., Mo., and Tex. (S. Am.)