Commelina benghalensis L.
Benghal dayflower, dayflower, tropical spiderwort, jio, wandering-Jew
Fruit a capsule with 2 seeds. Seeds dimorphic. Subterranean seeds elliptic to ovate in outline, 2–3.5 mm long, 1.3–2.1 mm wide, 0.8–1.1 mm thick, with two sides, one side convex, the other flat. Convex side with broad transverse ridges and a distinct round embryotega (cap covering embryo) located midlength, adjacent to edge, often with a central tubercle. Flat side smooth with a central raised ridge (hilum), and a short shallow groove extending transversely from embryotega. Testa dull, cream, silvery, light yellow/orange, or grey, mottling often reveals reticulations; reticulations small and/or large shallow honeycomb-sculpturing often differently colored. Surface sprinkled with minute tubercles, appearing sugar coated. Embryotega sometimes papillate. Hilum a narrow ridge about half the length of the flat side. Embryo small, straight, beneath embryotega; endosperm copious. Aerial seeds similar to subterranean seeds but truncate and smaller, 1.5–2.5 mm long, 1–2 mm wide, 0.8–1.1 mm thick.
widely distributed in tropical and subtropical Africa, central, southern and Southeast Asia extending to China, Japan, the Philippines, Australia, and Micronesia. In the western hemisphere, found in Cuba, Jamaica, Brazil, and United States
tropical and subtropical lowlands, moist conditions, sandy or rocky soils; a weed of cultivated lands, field borders, wet pasturelands, banks of irrigation ditches, gardens, roadsides, waste places
Commelina benghalensis is a creeping annual or perennial herb, up to 40 cm long, commonly forming dense, pure stands. It has become a serious weed of many crops in many countries worldwide, and is a particular problem in Africa. Grows best in moist places, but can withstand flooding and waterlogged conditions, as well as fairly dry conditions. It can reproduce vegetatively by rooting at the nodes of stems. Broken stems resulting from cultivation will also root, making C. benghalensis difficult to control.
A, subterranean seed showing embryotega; B, subterranean seed showing hilum; C, subterranean seed longitudinal section showing embryo, D, subterranean seed longitudinal section; E, aerial seed; F, aerial seed showing hilum, G, aerial seed longitudinal section showing embryo; H, aerial seed longitudinal section; drawing by Lynda E. Chandler