Oryza punctata Kotschy ex Steudel
Family Poaceae, Tribe Oryzeae
Disseminule (floret with 2 sterile lemmas) elliptic to oblong, ca. 4.5–9.2 mm long, 1.9–2.6 mm wide; callus smooth; disarticulation scar centric or slightly eccentric. Sterile lemmas similar, glume-like, linear, glabrous, 1–2 mm long. Rachilla internode not pronounced below fertile lemma. Fertile lemma and palea strongly laterally compressed, keeled, cartilaginous, surface scaberulous and tuberculate in a grid pattern. Lemma 4.5–9.2 mm long, 5-nerved; its margins inrolled, interlocking palea margins; with apical awn 10–75 mm long, slender, straight, antrorsely barbed. Caryopsis lanceolate or oblong, 4–4.8 mm long, 1.5–1.8 mm wide, oblong, laterally compressed, reddish; hilum linear, as long as caryopsis.
The wild red rices (Oryza longistaminata, O. punctata and O. rufipogon) can be distinguished from O. sativa L. (cultivated rice) by their red caryopses, although it may be difficult to differentiate the wild red caryopses from commercial rice cultivars with red grains.
Oryza punctata can be distinguished from O. rufipogon and O. longistaminata by its shorter fertile florets, rachilla not pronounced between the sterile lemmas, awns relatively slender and flexuous, and spikelets transversely (not obliquely) attached to pedicel.
Oryza longistaminata A. Cheval. & Roehr.
Oryza rufipogon Griff.
native to tropical Africa, South Africa, and Madagascar
introduced into Thailand
flooded watercourses, stream banks, pond margins, rice fields
Oryza punctata is a tufted annual grass, to 120 cm tall. See comments about the weediness of the wild red rices in the Oryza rufipogon fact sheet.