Biosystematics of Indian plants. II. The Problem of Centaurium pulchellum complex

Abstract

The genusCentaurium is represented in Amritsar District by three types of plants, distinguishable chiefly on the basis of flower-colour. The three races possess different chromosome numbers: white, n=18; purple, n=27; and cosmos, n=28. A new basic number, 9, has been found to exist in the genus. The white-flowered (4x) and purple-flowered (6x) races are, in all probability, alloploid in character. The exact nature of the cosmos-flowered race (n=28), however, is not known at present. It may either be an octoploid on the basic number 7, or a secondary polyploid from the hexaploid of x=9 (2n=56=6x + 2=54=2). All the three colour-forms have been referred to E. ramosissima Pers. now called C. pulchellum (Sw.) Druce by most taxonomists. However, the present investigation reveals that none of the races conforms strictly to this or to any other Indian species described by Hooker (1883). It appears that all or most of these species have arisen after extensive interspecific hybridization, which has resulted in a complete reticulation of characters. Furthermore, C. pulchellum in itself is a complex withn=10, 18, 20, 27, 28. In order to have a clear picture of the relationships of the Indian formsvis-a-vis their European counterparts, it is essential to conduct a well-planned biosystematic investigation based on samples from the entire range. The taxonomic tangle and synonymy needs to be clarified by reference to the type material.