Detection of Hexaploid and Mechanisms of Polyploidy Formation in Allium wallichii Kunth Intraspecific differentiation of Allium wallichii (Amaryllidaceae) inferred from chloroplast DNA and internal transcribed spacer fragments Diploid and Tetraploid Distribution of Allium wallichii Kunth(Ailiaceae) in the Yunnan-Guizhou Plateau Studies on the Karyotype of 5 Samples of Allium Sect. Bromatorrhiza Ekberg