We must therefore assume that, in the higher colony-forming plants, germ-plasm is contained in a great many cells, perhaps in all which are not histologically differentiated, and sometimes even in those which are so, as, for instance, in the leaves of Begonias. I suppose, therefore, that in the higher plants the process of development implies a segregation of the determinant-complexes of the germ-plasm, but that this takes place at a late stage, and that in a much higher degree than among animals the individual or the 'person' carries with it germ-plasm in a latent state. To this must be attributed the fact that the plant is not only able to make good its losses in twigs and branches by sending out new shoots, but that cuttings, that is, detached shoots, are also able to take root, and in general to give rise to what is necessary to complete themselves according to the position of the part in question. In the ontogeny of animals, too, we must assume that it requires a liberating stimulus to rouse the determinants to activity, that this stimulus is to be sought for in the influence exercised by the constitution of the cell on the idioplasm contained within it, and that this constitution in its turn is subject to influences from external conditions, including the cell-soma itself. We may therefore suppose that, among plants also, the germ-plasm latent in numerous cells only becomes active in whole or in part according to the influences exerted on it by the state of the cell at the moment; but this varies with external circumstances, according to whether the cell is exposed to light or lies under ground, according as it is influenced by gravity, by moisture, chemical stimuli, and so on.