And now we are prepared for entering on a still-remaining question respecting the structure of Phænogams--what is the origin of axillary buds? As the synthesis at present stands, it does not account for these; but on looking a little more closely into the matter, we shall find that the axillary buds are interpretable in the same manner as the terminal buds. So to interpret them, however, we must return to that process of proliferous growth with which we set out, for the purpose of observing some facts not before named. _Delesseria hypoglossum_, Fig. 105, represents a seaweed of the same genus as one outlined in Fig. 40; but of a species in which proliferous growth is carried much further. Here, not only does the primary frond bud out many secondary fronds from its mid-rib; but most of the secondary fronds similarly bud out several tertiary fronds; and even by some of the tertiary fronds, this prolification is repeated. Besides being shown that the budding out of several fronds from one frond, may become habitual; we are also shown that it may become a habit inherited by the fronds so produced, and also by the fronds they produce: the manifestation of the tendency being probably limited only by failure of nutrition. That under fit conditions an analogous mode of growth will occur in fronds of the acrogenic type, like those we set out with, is shown by the case of _Metzgeria furcata_, Figs. 45, 46, in which such compound prolification is partially displayed. Let us suppose, then, that the frond _a_, Fig. 106, produces not only a single secondary frond _b_, but also another such secondary frond _b′_. Let us suppose, further, that the frond _b_ is in like manner doubly proliferous: producing both _c_ and _c′_. Lastly, let us suppose that in the second frond _b′_ which _a_ produces, as well as in the second frond _c′_ which _b_ produces, the doubly-proliferous habit is manifested. If, now, this habit grows organic--if it becomes, as it naturally will become, the characteristic of a plant of luxuriant growth, the unfolding parts of which can be fed by the unfolded parts; it will happen with each lateral series, as with the main series, that its successive components will begin to show themselves at earlier and earlier stages of development. And in the same way that, by dwarfing and generalizing the original series, we arrive at a structure like that of the terminal bud; by dwarfing and generalizing a lateral series, as shown in Figs. 107–110, we arrive at a structure answering in nature and position to the axillary bud. [Illustration: Figs. 107–110.]