Morphological comparison of Asarum sect. Asiasarum (Aristolochiaceae) in Japan with special reference to multivariate analyses of flowers

In order to clarify the morphological variation of plants belonging to Asarum sect. Asiasarum in Japan, we performed extensive field examinations for 55 populations covering both geographic range, taxa, and morphological races hitherto recognized. As previous studies were not enough in evaluation of quantitative characters, we performed multivariate analyses of various floral quantitative characters in addition to new qualitative floral characters, together with those used in the previous studies. As a result, eight morphologically distinct forms were recognized. They were first divided into two groups by color patterns in the inner surface of calyx tube; form D is dark purple, form L is dark purple proximally, ivory white, yellowish green or light purple in the middle part, dark purple or white at the throat. Form D is further divided into D1-D4 by the number of cells of trichomes in the adaxial surface of calyx and by the number of stamens and pistils. Form L is further divided into L1-L4 by the shape of calyx tube, the width of calyx tube throat, and the size and shape of calyx lobes. The eight forms were distributed almost allopatrically, and were concluded to be worthy to be recognized as distinct taxa.