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Ten species of Datura L i n n. are found widely distributed in India (cf. Wealth of India 1952), and about twenty races of D. mete1 L i n n. has been recorded by B e r g n e r (1943). The authors in their screening project of several Indian species and races of Datura observed some interesting findings, which were subsequently verified by studying the cultures and crosses for over a period of three years. Some of the findings are presented in this paper. E v a n s and S t e v e n s o n (1962) record variations in the proportions of hyoscyarnine and hyoscine in the aerial parts of Datura leichhardtii. Further, Ev a n s and G r i f f i n (1964) noticed the presence of ditigloyl esters of the hydroxytropanes in the transpiration stream of D. innoxia and D. cornigera, even though ditigloyl is a common occurence in the roots of various Datura species. Later E v a n s (1963) elucidated the nature of alkaloid mixture contained within the roots of various Datura species. C h a n W e n-N u e i and S t a b a (1965) report that in tissue cultures the callus of seeds of D. stramonium and D. innoxia contains more alkaloids than the root, stem or leaf callus, while B u r d y k i n aS h e k h t a r (1966) records some observations on the mechanism of the origin of alkaloids in D. innoxia. The present study reports the seasonal periodicity, effects of polyploidy and altitudinal factors on the production of alkaloids in Datura species. Material and Methods T h e plants were cultured from seeds obtained from various localities in India. Haploid, ' diploid and tetraploids of Datura species were prepared in cultures by chemical treatments (colchicine etc.). All species were cytologically investigated by modified Bellings' ironacetocarmine techniques (cf. B l a k e s l e e , 1959).

The leaves of Tylophora asthmatica are used in Ayurvedic System of Medicine. Phytochemical investigation of 17 species of Tylophora have been recorded in this paper. I t is found that seventeen species under study show the presence of alkaloids, fiavonoids, sterol and tannins.Further from the study it is observed that the total percentage of Tylophorine is comparatively high during the'flowering periods. This factor can be fully exploited for commercial use.