there remains only a foliar surface (127), which, though often larger than the immediately-preceding foliar surface, shows failing nutrition by absence of chlorophyll. And then, in the quite terminal organs of fructification (129), we have the foliar part itself reduced to a mere rudiment. Though these progressive degenerations are by no means regular, being in many cases varied by adaptations to particular requirements, yet it cannot, I think, be questioned, that the general relations are as described, and that they are such as the hypothesis leads us to expect. Nor are we without a kindred explanation of certain remaining traits of foliar organs in their least-developed forms. Petals, stamens, pistils, &c., besides reminding us of the primordial fronds by their diminished sizes, and by the want of those several supplementary parts which the preceding segments possess, also remind us of them by their histological characters: they consist of simple cellular tissue, scarcely at all differentiated. The fructifying cells, too, which here make their appearance, are borne in ways like those in which the lower Acrogens bear them--at the edge of the frond, or at the end of a peduncle, or immersed in the general substance; as in Figs. 128 and 129. Nay, it might even be said that the colours assumed by these terminal folia, call to mind the plants out of which we conclude that Phænogams have been evolved; for it is said of the fronds of the _Jungermanniaceæ_, that, “though under certain circumstances of a pure green, they are inclined to be shaded with red, purple, chocolate, or other tints.” As thus understood, then, the homologies among the parts of the phænogamic axis are interpretable, not as due to a needless adhesion to some typical form or fulfilment of a predetermined plan; but as the inevitable consequences of the mode in which the phænogamic axis originates.