Studies on the menispermaceæ

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Summary

1. Cytological study has been made of the staminate plants of six species belonging to six genera and three tribes of the Menispermaceæ.

2. The chromosome counts made in them aren=13 and 2n=26 inTinospora cordifolia, 2n=26 inAnamirta cocculus, n=13 inTiliacora racemosa, n=13 and 2n=26 inStephania rotunda, n=12 and 2n=24 inCissampelos pereira andn=24 and 2n=48 inCyclea peltata.

3. From a discussion of all the available cytological data on the Menispermaceæ it is suggested that the existing basic chromosome numbers in the family are 12 and 13, of which 13 is the most common.

4. Taxonomic relationships of the family are briefly discussed in the light of cytological findings, and it is suggested that the ancestors of the present-day Menispermaceous genera with basic numbers 12 and 13 might have originated from more than one genus in the Berberidaceæ with 6 and 7 as their basic numbers.

5. Chromosome size variation in the family is briefly considered and together with data on floral morphology it is suggested thatStephania should be transferred from the tribeCissampelideæ to the tribeCocculeæ.

6. Unequal pairs of chromosomes were seen in the male plants ofStephania rotunda andCissampelos pereira. Heteropyknosis was found in one of the chromosomes in the male plants ofTinospora cordifolia. These male plants are provisionally suggested to be heterogametic with XY type of sex chromosomes.

Communicated by Professor A. Abraham,f.a.sc.