It was pointed out in § 196, that the terminal folia of a phænogamic axis have sundry characters in common with such fronds as those out of which we concluded that the phænogamic axis has arisen by integration--common characters of a kind to be expected. In their simple cellular composition, comparative want of chlorophyll, and deficiency of vascular structures, the undeveloped ends of leaf-shoots and the developed ends of flower-shoots, approach to the fronds of the simpler Archegoniates. We also noted between them another resemblance. It is said 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;” and answering to this we have the facts that such colours commonly occur in the terminal folia of a phænogamic axis, when arrest of its development leads to the formation of a flower, and that very frequently they are visible at the ends of leaf-axes. In the unfolding parts of shoots, more or less of red, or copper-colour, or chocolate-colour, may generally be seen: often, indeed, it characterizes the leaves for some time after they are unfolded. Occasionally the traces of it are permanent; and, as in the scarlet terminal leaves of _Poinsettia pulcherrima_, we see that it may become, and continue, extremely conspicuous. The question, then, now to be asked is--has this colouring by which the immature part of the phænogamic axis is characterized, anything to do with the colouring of flowers? Has this difference between undeveloped folia and folia that are further developed, been increased by natural selection where an advantage accrued from it, until it has ended in the strong contrast we now see? I think we may not irrationally infer that this has happened.