台灣植物誌 第二版 Flora of Taiwan, 2nd edition Vol. 1
4. ISOETACEAE 水韭科
DEVOL, CHARLES E.
Usually aquatic perennials, growing submersed, emersed or rarely terrestrial; stem corm-like,2-4 lobed giving rise to numerous dichotomously branching roots and a tuft of elongated grass-like leaves. Leaves with 4 longitudinal air-channels and a central vascular strand, some species with peripheral vascular strands, many species with stomata. Sporangia large, borne at base of sporophylls, containing either large tetrahedral megaspores, or minute ellipsoidal microspores; ligule borne above
sporangium; a thin velum often more or less covering the sporangium; basal portion of sporophylls expanded, winged. Megaspores white, gray or black, smooth, warty, echinate or reticulate.
A family with only one genus.
1. ISOETES L. 水韭屬
Characters of the family.
About 100 species, and many varieties, only one species in Taiwan.
1. Isoetes taiwanensis DeVol in Taiwania 17(1): & (2): 304. 1972; in Fl. Taiwan 1: 53. pl. 11. 1975. 台灣水韭 Pl.14, Photo 38
Corms 3-4 lobed. Leaves widely spreading, 7 to 24 cm long, in tufts of 15 to 90 or more, flattened on upper side, rounded on lower side, the base expanded with membranaceous margins, with scattered stomata near the tips, peripheral fibers absent; ligule elongate, triangular; velum rudimentary, only covering top of the sporangium. Megasporangium oval; megaspores gray when wet, white when dry, rugulate on basal side, other sides of megaspores tuberculate, 280 to 390 μ in diameter; microspores gray, elliptic, with small spines, 25 x 15 μ.
Only known from Taiwan. Growing in shallow ponds, submersed most of the year.
TAIPEI: Chonghu(Chihsingshan), Hsu & Chang 1715, DeVol 8005*, Huang 13558.