- Flora, Bd. 167, S. 423-431 (1978) Floral Features of Solanum macranthum DuN. with Special Reference to Stylar Heteromorphism and Intercrossability SHAMIM BAKSH and MuHAMMAD IQBAL Botany Department, Aligarh Muslim University, Aligarh · 202001, India Summary Various interesting aspects of floral biology have been studied in Solanum macranthum Dun. as a prelude to breeding programme. On the basis of the style length variation, 3 types of flowers have been identified. Results of crosses among the different flower types reveal that the long, and medium style flower are male as well as female fertile while the short style flowers only male fertile. Relevant features of these flower types have been analysed on a comparative basis. The biological significance of the stylar heteromorphism in Solanums is discussed in relation to adaptation and phylogeny, and the probable cause of the phenomenon speculated upon. Introduction Solanum melongena L., the egg-plant, is widely cultivated in the warmer regions of the world. Most of the cultivated varieties are susceptible to various insect pests and fungal or viral diseases, such as leaky fruit rot, phomopsis blight, early blight, little leaf and leaf mosaic (see KRISHNAIAH and VIJAY 1975). On the other hand, there are many species of Solanum that have shown considerable resistance against diseases and insect pests. Such an example is Solanum macranthum Dun., an ornamental woody species with large bluish flowers, which has been found to be highly resistant to shoot and fruit borers as well as to various diseases under field conditions. It can, therefore, prove a good source of genes for resistance which can be transferred by hybridization to the susceptible cultivated varieties of egg-plant. Before we embark on an exten- sive hybridization programme it is wise to have an understanding of the major aspects of floral biology of the plants to be used. Although various aspects of the floral biology of egg-plant have been worked out, nothing is virtually known regarding that of S. macranthum. It is germane to mention here that although the "heterostyly" i.e. the occurrence of flowers with different style length, accompanied by differences in size of stamens, pollens and stigmatic papillae, on different individuals of the same species has long been known (see DARWIN 1888), a new term "stylar heteromorphism" has recently been coined by HossAIN (1973) and corroborated by BAKSH et al. (1977) for a similar phenomenon i.e. the occurrence of flowers with stylar variation on the same inflores- cence, branch or plant. This term is frequently used in the present study which reveals certain important floral features with special attention to the stylar length variation in Solanum macranthum.