An Illustrated Flora of the Northern United States, Canada and the British Possessions/Vallisneriaceae
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Anal. Fam. 54.
Submerged or floating aquatic herbs, the leaves various. Flowers regular, mostly dioecious, appearing from an involucre or spathe of 1-3 bracts or leaves. Perianth 3-6-parted, the segments either all petaloid or the 3 outer ones small and herbaceous, the tube adherent to the ovary at its base in the pistillate flowers. Stamens 3-12. Anthers 2-celled. Ovary 1-celled with 3 parietal placentae. Styles 3, with entire or 2-cleft stigmas. Ovules anatropous or orthotropous. Fruit ripening under water, indehiscent. Seeds numerous, without endosperm.
About 6 genera and 25 species of wide distribution in warm and temperate regions. Besides the following, another genus, Halophila, occurs on the coast of Florida.
|•||Stem branched ; leaves whorled or opposite.||1.||Philotria.|
|•||Acaulescent ; stoloniferous ; leaves grass-like, elongated.||2.||Vallisneria.|
Stems submerged, elongated, branching, leafy. Leaves opposite or whorled, crowded, 1-nerved, pellucid, minutely serrulate or entire. Flowers dioecious or polygamous, arising from an ovoid or tubular 2-cleft spathe. Perianth 6-parted, at least the 3 inner segments petaloid. Staminate flowers with 9 stamens, the anthers oblong, erect. Ovary 1-celled with 3 parietal placentae. Stigmas 3, nearly sessile, 2-lobed. Fruit oblong, coriaceous, few-seeded. [Name from the Greek, referring to the leaves, which are often whorled in three's.]
About 10 American species. Type species Elodea canadensis Michx.
|•||Leaves oblong or ovate-oblong, mostly obtuse; staminate flowers unknown.||1.||P. canadensis.|
|•||Leaves linear or oblong, acute; hermaphrodite flowers unknown.|
|•||Leaves oblong or linear-oblong, 1″–1½″ wide wide; spathe of the staminate flowers 2½″–3″ long, anthers 1″–1¼″ long.||3.||P. Nuttallii.|
|•||Leaves linear, rarely 1″ wide; staminate spathe 1″–1½″ long; anthers about ½″ long.|
|•||Leaves 5″–10″ long; sepals and petals ¾″–1″ long.||2.||P. angustifolia.|
|•||Leaves 2½″–4″ long; sepals and petals ½″–¾″ long.||4.||P. minor.|
Aquatic dioecious submerged perennials, with long grass-like floating leaves. Staminate flowers with a 2-3-parted spathe on a short scape, numerous, nearly sessite on a conic receptacle; perianth 3-parted; stamens generally 2 (1-3). Pistillate flowers on a very long flexuous or spiral scape, with a tubular, 2-cleft, 1-flowered spathe; perianth-tube adnate to the ovary, 3-lobed and with 3 small petals; ovary 1-celled with 3 parietal placentae; stigmas 3, nearly sessile, short, broad, 2-toothed with a minute process just below each sinus; ovules numerous, borne all over the ovary-wall, orthotropous. Fruit elongated, cylindric, crowned with the perianth. [Named for Antonio Vallisneri, 1661-1730, Italian naturalist.]
A genus consisting of 2 species, the one of wide distribution both in the Old World and the New, the other confined to the Gulf States. Type species : Vallisneria spiralis L.