Abstract: Dendranthema indicum L. and D. lavandulifolium (Fisch. ex Trautv. ) Ling et Shih are two species which are greatly variable in morphology. The specimens collected from different habitats show distinct variation in characters such as leaf division、 leaf pubescence、 size of capitula and number of capitula. Some authors (Li 1983; Du 1989; Nakata 1987)have studied the chromosome numbers and karyotypes of D. indicum and D. lavandulifolium and reported the basic chromosome number and polyploidy of these two species. But some questions, such as the patterns and trends of morphological variation, the relationships between morphological and karyotypical variations and the phylogenetic relationship between D. indicum and D. lavandulifolium remain unclear . Based on wide field investigation and cultivation experiments, the present authors made a thorough study on D. indicum and D. lavandulifolium from morphology、 cytology with reference to geographical distribution and habit conditions. The results show that the amount of leaf pubescence of D. indicum is closely related to the water content in its habitat; the diameter of capitula decreases, while the number of capitula of D. lavandulifolium increases with the increase in elevation. Comparing the karyotypical constitution of different populations of D. indicum and D. lavandulifolium, the authors infer that natural hybridization, both intraspecific hybridization and hybridization between D. indicum and D. lavandulifolium, has played an important role in the origin of polyploids and in the evolutionary process of karyotypes of D. indicum and D. lavandulifolium. By a synthetic analysis from morphology, cytology and geography, the authors also suggest that D. indicum and D. lavandulifolium be sister species, derived from a common ancestor, and it is unreasonable to consider one of themevolved from the other.

Key words: D. indicum, D. lavandulifolium, Morphological variation, Karyotype