Page:The Journal of Indian Botany.djvu/214

i80 THE JOUENAL OP INDIAN BOTANY. from certain of the Lobelideae in which the calyx may have been entirely absent. Yet another instance is the formation of the reserve food (endosperm) of the angiosperm seed out of apparently a second embryo which has been spoilt by the fusion of its nucleus with the polar nucleus, in order to replace the gametophyte, which, reduced in Gymnosperms, had dis- appeared perhaps with the necessity for limiting the size of the ovules in the closed carpel. The peculiar secondary thickening of the larger Monocotyle- dons and the polystely of Ganera may be explained on the same lines i.e. that the original mode of thickenning has been lost, and when in the course of evolution the necessity for a thicker stem again arose, had to be replaced by a different method. On this hypothesis too she suggests, that the floral envelope of Naia is not a reduced perianth, still less a rudimentary one, but a new structure evolved to take the place of a lost perianth. The new Law is thus in accord with the view that the primitive angiosperm flower was of the type now in the Ranales, and is not to be found among the Archiohla- mydeae, as assumed in the ' continental ' systems of Eichler and Engler, and affords pleasing support for the older system of the Qenera Plantar rum of Bentham and Hooker, in so far at least that in it the Ranunciilaccic were placed first, and the apelalae last of the Dicotyledons with the Monoco- tyledons after. Mrs. Arber supports her hypothesis with instances drawn from the evolution of animals, in which the Law of Loss had previously been enunciated in another form. The essay is most interesting and suggestive, and well worth attention. It is in conformity with the idea of the absolute- ness of inheritance, towards which so much modern work seems to point.

P. F. F.

McLean, R. C. Sex and Soma.

This was the title of a communication read at a meeting of the Liuhaean Society on November 20th, 1919, with reference to the occurrence of multinu- cleate cells in higher plants, as described especially by Dr. Arber and Dr. Beer, in a paper which was abstracted in the November issue of this journal, p. 94. The papers has not appeared in print, and the following is taken from the published minutes of the meeting.

" The Author enlarged upon the recently discovered phase of multinuc- leosis in the developing soma cell of higher plants .... and maintained, in opposition to Arber and Beer, that there is evidence of nuclear reunions taking place in the multinuclear cells. He characterized these fusions as modified sexual conjugations consequent upon the long series of vegetable divisions in the lineage of a soma cell, and necessary to avoid the degeneration which experiment shows to be attendant upon prolonged vegetative propagation. The development of the plant body may thus be regarded as embracing two phases of stimulus : firstly, the normal sex stimulus which initiates the period of maximum cell proliferation, and, secondly, this somatic nuclear union, initiating the period of maximum differentiation. Tissue differentiation, it was suggested, may be associated with some process of segregation subse- quent to this nuclear fusion ... It was finally suggested that germinal modifications as well as somatic segregations may be derived from a mecha- nism of nuclear fractiontzation and subsequent partial reunion in somatic

cells."

P. F. F.