槐 叶 苹 科 [Pin Yin]
Ferns, floating, small. Stems horizontal, slender, covered with hairs and protostele. Fronds sessile or very shortly stipitate; fronds 3, verticillate, two fronds floating on water surface, normally elongate, green, entire, hairy, and densely covered with papillae on upper surface, costae slightly distinct; other frond submersed and finally dissected and rhizoid (rootlike). Sori clustered at stipe bases of submersed fronds, or double attached along submersed ones; microsporocarp large and containing majority of microsporangia, each microsporangium containing 64 microspores; megasporangia flower-vase-shape, each one only containing one megaspore, trilete, experispore[??], with small retuse on exine; microspores sphaeropteroid[??], trilete mark finer, exine of mark usually retuse, triangular, experispore, exine thinner, smooth.
One genus: on all continents, mostly in American and African tropics.
Characters of the genus same as the family. x = 9.
About 10 species: widely distributed on all continents, mostly in American and African tropics. One species in China.
槐叶苹 huai ye ping
Marsilea natans Linnaeus, Sp. Pl. 2: 1099. 1753.
Stems covered with dark brown articulate hairs. Fronds 3, verticillate; two fronds normal, floating, ‘Robinia’-shaped, 0.8–1.4 × 0.5–0.8 cm, base rounded or subcordate, entire, apex obtuse; stipe ca. 1 mm or fronds sessile. Venation obliquely spreading, veinlets 15–20 pairs on either side of costa, each one with 5–8 bunches of white setae. Fronds herbaceous, deep green adaxially, densely brown villous abaxially; submersed fronds finally dissected into linear segments, covered with hairs, rootlike and acting as roots. Sporocarps 4–8, clustered at bases of submersed leaves, with sparse bunches of hairs; microsporocarps yellowish, megasporocarps brownish.
Floating on rice fields, ponds, ditches, widely distributed in valleys and regions of Changjiang. N and NE China [list provinces??Anhui, ??Fujian, ??Hebei, ??Henan, ??Jiangxi, ??Liaoning, ??Shanxi, ??Zhejiang], Taiwan, Xinjiang [India, Vietnam; Africa, Asia, Europe].
The whole plant is used as medicine; it is boiled and eaten for consumptive disease and eczema, and externally used for inflammatory diseases with redness of skin, furuncles, and scalds.
The name Salvinia natans has been misapplied to plants in North America (Salvinia minima Baker).