Spadix cylindrical, lateral, sessile, emerging from the side of a simple 2-edged scape which resembles the leaves, densely covered with perfect flowers. Sepals 6, concave. Stamens 6; filaments linear; anthers kidney-shaped, 1-celled, opening across. Ovary 2–3-celled, with several pendulous orthotropous ovules in each cell; stigma minute. Fruit at length dry, gelatinous inside, 1–few-seeded. Embryo in the axis of albumen.—Pungent aromatic plants, especially the thick creeping rootstocks (calamus of the shops), which send up 2-edged sword-like leaves, and scapes somewhat like them, bearing the spadix on one edge; the upper and more foliaceous prolongation sometimes considered as a kind of open spathe. (Ἄκορας, the ancient name, of no known meaning.)
1. A. Cálamus, L. Scape leaf-like and prolonged far beyond the (yellowish-green) spadix.—Margins of rivulets, swamps, etc., N. Scotia to Fla., west to Minn., Iowa, and E. Kan.
Order 124. LEMNÀCEÆ. (Duckweed Family.)
Minute stemless plants, floating free on the water, destitute of distinct stem and foliage, being merely a frond, producing one or few monœcious flowers from the edge or upper surface, and commonly hanging roots from underneath; ovules rising from the base of the cell. Fruit a 1–7-seeded utricle. Seed large; the apex or radicular extremity of the seed-coat separable as an operculum or lid (as in Cabomba, etc.). Embryo straight, surrounded by fleshy or sometimes very scanty albumen.—The simplest, and some of them the smallest of flowering plants, propagating by the proliferous growth of a new individual from a cleft in the edge or base of the parent frond, remaining connected for some time or separating, also by autumnal fronds in the form of minute bulblets, which sink to the bottom of the water, but rise and vegetate in spring; the flowers (in summer) and fruit scarce, in some species hardly ever seen. Frond more or less cavernous; the upper surface furnished with stomata.—These plants may be regarded as very simplified Araceæ.
1. Spirodela. Frond 7–11-nerved, with several rootlets.
2. Lemna. Frond 1–5-nerved, with a single rootlet.
3. Wolffia. Frond thick, very minute (¼–{2/3}´ broad), without rootlets.
1. SPIRODÈLA, Schleiden.
Anther-cells bilocellate by a vertical partition and longitudinally dehiscent. Ovules 2. Frond 7–11-nerved or more; rootlets several, with axile vascular tissue. Otherwise as Lemna. (From σπεῖρα, a cord, and δῆλος, evident.)
1. S. polyrrhìza, Schleid. Fronds round-obovate (2–4´´ long), thick, purple and rather convex beneath, dark green above, palmately (mostly 7-) nerved. (Lemna polyrrhiza, L.)—Very common in ponds and pools, throughout N. Am., but very rarely found in flower or fruit. (Eu.)