Abstract
We recognize a new peloric form of the orchid Cephalanthera falcata (Thunb.) Blume f. conformis Hiros. Hayak. et J. Yokoy., which occurs in the vicinity of the Tsukuba mountain range in Ibaraki Prefecture, Japan. This peloric form is sympatric with C. falcata f. falcata. The peloric flowers have a petal-like lip. The flowers are radially symmetrical and the perianth parts spread weakly compared to normal flowers. The stigmas are positioned at the column apex, thus neighboring stigmas and the lower parts of the pollinia are conglutinated. We observed similar vegetative traits among C. falcata f. falcata, C. falcata f. albescens S. Kobayashi, and C. falcata f. conformis. The floral morphology in C. falcata f. conformis resembles that of C. nanchuanica (S.C. Chen) X.H. Jin et X.G. Xiang (i.e., similar petal-like lip and stigma position at the column apex; syn. Tangtsinia nanchuanica S.C. Chen), but C. falcata f. conformis and C. nanchuanica can be distinguished by their staminodes (5 inconspicuous staminodes in the former, and 3 large and 2 inconspicuous staminodes in the latter). Nucleotide sequences of nrDNA ITS and cpDNA trnL-F intergenic spacer regions of C. falcata f. conformis were different from those of C. nanchuanica. The two peloric taxa likely have independent origins, although both are derived from C. falcata.
