Lastly, the explanation of the canals as threads of vegetation fays in with the one which has been found to meet the requirements of the blue-green areas; while the fact that they prove to develop as they do, reversely to what would take place on earth, is exactly what all we have latterly learnt about the surface conditions of the planet would lead us to expect. From what has just been said we see that the latest observations at Flagstaff confirm the earlier ones, and, what is especially corroborative, they do so along another line. The former were chiefly static, the latter kinematic. In other words, the behavior of the canals in action bears out the testimony of their appearance at rest. CHAPTER XXIX LIFE Study of the fundamental features of Martian topography has disclosed, as we have seen, the existence of vegetation on the planet as the only rational explanation of the dark markings there, considered not simply on the score of their appearance momentarily, but judged by the changes that appearance undergoes at successive seasons of the Martian year. Thus we are assured that plant life exists on the planet. We are made aware of the fact in more ways than one, but most unanswerably for that trait to which vegetation owes its very name,—its periodic quickening to life. Thus the characteristic which has seemed here most distinctive of this phase of the organic, so that man even christened it in accordance, has proved equally telltale there. Important as a conclusion this is no less pregnant as a premise. For the assurance that plant life exists on Mars leads to a further step in extramundane acquaintance of far-reaching import. It introduces us at once to the probability of life there of a higher and more immediately appealing kind, not with the vagueness of general analogy, but with the definiteness of specific deduction. For the presence of a flora is itself ground for suspecting a fauna.