Classificatie en sexualiteit bij Taraxacum

The history of classification of the genus Taraxacum is shortly discussed and attention is paid to the significance of the taxonomical and phytogeographical studies of Professor Van Soest. The mode of reproduction and the occurrence of sexuality and hybridization in Europe is described. The results of an investigation of sexuality in about 70 populations found in the northern parts of Switzerland and Austria and in the southern part of Germany (B.R.D.) are concisely reported. It appears that sexuals are of common occurrence in this area and that there is a transitional zone from about Stuttgart to Passau in which the diploids in the populations are gradually replaced by polyploids. The diploids belong to the section Vulgaria and include a great number of forms. It is unknown whether these forms are the products of hybridization or if they indeed belong to genetically isolated (micro)species. The causes of the distribution of the diploid sexuals are unknown. They appear to have a slight preference for less disturbed habitats as compared with the polyploids. The transition from the diploids to polyploids in the populations may be caused by a more intensive agriculture in the area concerned and by climatic factors and may be influenced by historic phytogeographical factors. The distribution of the diploids and polyploids is shown in fig. 1; the percentage of the diploids are indicated in black, the polyploids in white.