Isachne myosotis Nees

It grows on moist ground and newly exposed soil along ditches at low altitudes.

This small species is recognizable on account of its delicate, mat-forming habit, small, broad leaf blades, smooth panicle branches, and tiny spikelets. It is barely separable from Isachne pauciflora.

Culm creeping, branching and routing at the basal nodes. Blade membranous, lanceolate; sparingly pilose; sheath laterally compressed, densely hispid, less than 1/2 as long as the internode; ligule a ring of hairs, about 0.6 mm long. Inflorescence a deltoid, loose, open panicle, branchlets filiform, with only a few spikelets. Spikelets about 1.4 mm long, broadly elliptical, pubescent; glumes nearly equal, 3-7-nerved, equaling the spikelet, obtuse, hispid, usually with a few stiff hairs toward the apex. Florets similar in appearance, about 1 .2 mm long, more or less pubescent; rachilla about 0.2 mm long.

Small mat-forming annual. Culms very slender, prostrate, branching and rooting at nodes, flowering branches up to 10 cm tall. Leaf sheaths thinly to densely hispid with spreading hairs, or hairs confined to margins; leaf blades lanceolate-ovate, 1–2(–3) × 0.2–0.5 cm, both surfaces hispid, densely or sometimes inconspicuously appressed-hairy, base rounded, apex acute; ligule ca. 0.7 mm. Panicle ovate or contracted, 1.5–5 cm, eglandular, spikelets usually 15–30 (fewer in depauperate specimens); branches spiculate to base, with short stiff branchlets and pedicels, smooth. Spikelets subglobose, 1–1.4 mm, tinged purplish; florets similar; glumes equal to spikelet, separated by a short internode, ovate-oblong, 5(–7)-veined, hispid usually above middle, occasionally hispid almost to base or almost glabrous, apex obtuse; lemmas strongly convex, leathery, puberulous to densely pubescent. Fl. and fr. May–Oct. 2n = 20.

Distributed in Southern China, Taiwan to the Philippines.

Wet ground, shallow water in ditches. Fujian, Taiwan [Indonesia, New Guinea, Philippines].

Isachne debilis Rendle in Journ. Linn. Soc. 36: 322. 1904; Hayata, Icon. Pl.: Form. 7: 58. 1918, pro parte; Honda, 1. c. 278. 1930; Keng, 1. c. 647. f. 584. 1959; Hsu in Taiwania 16: 271. 1971, Taiwan Grass. 469. pl. 129. 1975
Isachne monticola Hack. in Bull. Herb. Boiss. 7: 528. 1899; Honda, l. c. 281. 1930.

Isachne micrantha Merrill; I. myosotis var. micrantha (Merrill) Jansen; I. myosotis var. minor Honda; I. nipponensis var. minor (Honda) Nemoto.