Three new species of asarum (section heterotropa) from Taiwan

Three new species of Asarum L. sect. Heterotropa: A. chatienshanianum C. T. Lu & J. C. Wang, A. tawushanianum C. T. Lu & J. C. Wang, and A. villisepalum C. T. Lu & J. C. Wang, from Taiwan are described and illustrated. The somatic chromosome number and micromorphology of pollen grains of all of them were also examined. The somatic chromosome number in all three species is 2n=24. The tectum of the pollen is rugulate-perforate with large supratectate warts in A. tawushanianum and A. villisepalum but composed of perforated subunits in A. chateinshanianum. Asarum chatienshanianum and A. villisepalum are similar to A. macranthum Hook f. in gross morphology, but differ in floral morphology. Asarum chatienshanianum has greenish yellow flowers, a longer cylindrical calyx tube and the apex of the styles is bilobed. Asarum villisepalum is distinguished by dark maroon flowers, the densely white villous adaxial surface of the calyx lobes, and the internal surface of the calyx tube with 12 and 24 longitudinal ridges on the upper and lower part respectively. Asarum tawushanianum resembles A. hypogynum Hayata, but is distinguishable in having a short cylindrical calyx tube and smaller dark purple flowers. Descriptions, illustration and a synoptic key are provided for comparison with other species of Asarum in Taiwan.