Now, such contrariety of progression to what we should observe in the case of the earth could we view it from afar is exactly what the curves of visibility of the canals exhibit. Timed primarily, not to the return of the sun but to the advent of the water, vegetal quickening there follows, not the former up the latitudes but the latter down the disk. For better understanding, the two curves of phenological quickening, the mundane and the Martian, are shown in the diagrams. The plates represent the surfaces of the two planets, that of the earth being shown upside down with south at the top so as to agree with the telescopic depiction of the topography of Mars. The stars mark the epoch of the dead-point of vegetation at successive latitudes; the time increasing toward the right. The curves, it will be noticed, are bowed in opposite ways. The bowed effect is due in part to Mercator’s projection; in part it may represent a real decrease in speed with time. But what is strikingly noticeable is the opposite character of the advance to the right, the one curve running up the disk, the other down it. This shows that the development of vegetation proceeded in opposite directions over the surface. Thus is the opposed action upon the two planets accounted for, and we are led to the conclusion that the canals are strips of vegetation fed by water from the polar caps, and that the floral seasons there as affecting the canals are conditioned, not as they would be with us, directly upon the return of the sun, but indirectly so through its direct effect upon the polar snows. Once adventured on the idea of vegetation, we find that it explains much more than the time taken by the wave of canal-development down the disk. It accounts at once for the behavior of the canals in the three northern zones: the polar, arctic, and sub-arctic. The mean cartouches of these three zones dip down at their latter end instead of rising there, as is the case with the cartouches of the mean canals farther south. This dip denotes that the most northern canals were waning already by the middle of their August, though the others showed no such tendency; while the date of the deposition of the frost in these northern latitudes shows that they were started upon their course toward extinction before the snow itself had covered them. In other words, they were not obliterated but snuffed out. That their decline was thus preparatory to the coming of the first snowfall or frost-fall, sufficiently severe to whiten the ground so that it did not melt the next day, is suggestive of their constitution. It is clear that they were not abruptly cut off by the frost, but were timed by nature to such extinction. Vegetation would behave in just this way, since evolution would accommodate the career of a plant to its environment.