The Encyclopedia Americana (1920)/Vallisneria
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|Edition of 1920. See also Vallisneria on Wikipedia, and the disclaimer.|
VALLISNERIA, the typical genus of the tape-grass family. It is composed of aquatic plants, V. spiralis being the tape-grass or eel-grass, whose long submerged leaves are detested by swimmers; in Chesapeake Bay it is the “wild celery” upon the roots of which the canvasback feeds, and to which are due the admirable flavor of that duck. The leaves are very long and narrow, and float just under the surface in shallow water, the plant being rooted in mud or sand. It spreads widely by stolons, so that it often forms a wide belt along the shore, which is a great refuge for the small fry of water-life, but greatly impedes the passage of boats. Vallisneria is peculiar in its arrangements for cross-fertilization. The leaves are arranged in fascicles, from the axils of which spring the flowers, only one sex on each plant. They are enclosed in a kind of bladder formed by two membranous, concave bracts. There is only one pistillate flower to a bladder, and when ready for fertilisation, the envelope splits and frees this flower, its ovary elongates, and it is pushed upward by the growing stalk, until the whorl of three lanceolate sepals floats on the surface. Above them are three abortive petals, and three stigmas, by-lobed at the apices, and fringed on the edges. They project slightly between the sepals. In the meantime, the bladder about the staminate flowers, which are numerous, on a short axis, and have never risen far above the mud, becomes disrupted, and the flowers, which are globular, and have their three sepals closed tightly over the stamens, float like bubbles to the surface. There they drift about, and soon open. The arched sepals become reflexed, until they look like three boats tied close together at one end. Two stamens project obliquely from the point of union, tipped with masses of sticky pollen-cells. These tiny crafts are blown about by the winds, and carried by currents, on the surface of the water, sometimes covering it as with a creamy film. In the course of their travels, they almost inevitably strike against the waiting pistillate flowers, riding at anchor, with their three stigmas poised at exactly the angle to allow their fringes to detach the sticky pollen-masses from the other flower. As soon as the pollen adheres firmly to the stigmas, the pistillate flowers are withdrawn beneath the surface by the contraction of the long stalks, which assume a spiral form, and ultimately ripen fruit near the muddy floor of the stream.