VALLISNERIA (named after Antonio Vallisneri, 1661-1730, an Italian botanist, Professor at Padua). ORD. Hydrocharideae. A monotypic genus. The species is a half-hardy, aquatic, submerged herb, found in fresh-water lakes, ditches, &c. It is largely grown in aquaria in this country, and requires to be planted deeply in the water. VALLISNERIA spiralis (spiral). Eel Grass; Tape Grass. fl. white, minute, apparently forming an ovoid or globular head not quite so long as the dioecious, shortly bi--or trifid spathes. July. l. very long and narrow when the water is deep, short in shallow water, obtuse or acute and more or less minutely toothed at the ends, or sometimes perhaps quite entire Stems very short, sometimes stoloniferous. Warm and temperate regions, 1818. The male flowers are borne on a very short peduncle, and are sessile on a conical axis. At the flowering period, the female peduncle gradually lengthens, so that the flower finally floats on the surface of the water. Then the male submerged flowers detach themselves spontaneously from their peduncle and rise to the surface. After fertilisation, the peduncle of the female flower contracts spirally, and the ovary descends to the bottom of the water to ripen its seeds.