The study of the detailed cytology of Hibiscus mutabilis was undertaken with a view to ascertain whether the non-setting of seeds is due to the formation of abortive pollens, or to the degenerations in the embryo-sac.During the progress of our investigation we came across with some interesting details which seem to throw light on the role of the nucleolus, especially in this plant.We think it worth while to record in this short paper, our observations on the same. Previous WorkEver since Fontana discovered the nucleolus in 1781, various theories on its structure, function and importance have been put forward by competent observers as a result of critical examinations of both the plant and the animal cells. These have from time to time been reviewed by various authorities, such as, Walker and Tozer (28), Ludford (13), Wilson (27), Yamaha and Sinoto (30), Sharp (20), Schurhoff (21), Guillermond and Mangenot (11), de Mol (5), and Darlington (4), and we do not repeat them here. We will consider only those which have a direct reference to our observations. Since the time of Flemming (Wilson 27) a good many number of cytologists regard the nucleolus as a store-house of chromatin "destined to play some definite part in the later operations of the nucleus ('transportation hypothesis of Haeker') (Wilson 27 p. 95), and our observation points to the same conclusion.Among the recent works on the "Chromatin theories" of the

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