南国田字草 nan guo tian zi cao

Marsilea crenata C. Presl; M. sinensis Handel-Mazzetti.

Rhizomes creeping, with internodes up to 6.5 cm, but internodes frequently much shorter and fronds then appearing tufted; roots arising both at nodes and 1 or 2 on internodes, short shoots of 1-3 mm frequently formed at nodes; longer shoots sparsely pubescent to glabrate, short shoots often densely pubescent with pale reddish brown hairs ca. 1 mm. Stipes green to straw-colored, 6-16 cm, slender, glabrate; pinnae obtriangular to fan-shaped, 0.5-1.9 × 0.4-1.5 cm, glabrate adaxially, sparsely appressed-pubescent to glabrate abaxially, margin entire, bilobed, or crenate. Sporocarps 1 or 2 per frond, attached at base of stipe where stipe joins rhizome or up to 5 mm up stipe, often persistent after frond decay and appearing to arise directly from rhizome; peduncle 2.8-9.3 mm (when 2 sporocarps on a frond occasionally joined by a common peduncle ca. 1 mm), plus an additional 1.3-2.2 mm adnate to sporocarp, sparsely pubescent to glabrate; sporocarp brown to black, elliptical in lateral view, 2-4.9 × 1.8-3.9 × 1.2-2.5 mm, soft leathery, convex on lateral sides, obtuse to rounded on perimeter, usually marked with a distinct tooth 0.1-0.5 mm above end of peduncle, densely appressed-pubescent when young, becoming thinly pubescent to glabrate with age.

Rice fields, ponds, ditches; 100-1400(-2000) m. Anhui, Fujian, Guangdong, Guizhou, Hainan, Hubei, Hunan, Jiangsu, Jiangxi, Shaanxi, Sichuan, Taiwan, Yunnan, Zhejiang [paleotropics, plus sporadic introductions in the Americas and Caribbean (Brazil, Trinidad and Tobago, and SE United States)].

The whole plant is used for forage, and it is used medicinally for treating inflammation, edema, snakebites, and skin injuries.