disturbances of a deeper and universal state of forced equilibrium, which pervades the vital as it is known to pervade the mechanical world. And just as astronomers and physicists, confining their investigations to the more obvious and perceptible motions of celestial and terrestrial bodies, long remained ignorant of the law of gravitation which constantly forces all things into a state of equilibrium, so in biology the statical condition has been lost sight of in the effort to obtain better views of that moving panorama which a broader knowledge of the phenomena of life so unmistakably unfolds. Yet, without a clear recognition of this statical law, it is impossible to account for the facts presented by the distribution of plants, and it will doubtless be found equally essential to the full comprehension of many other phenomena of Nature. But, when we recognize this law, the whole aspect of our question is changed. Plants appear to be no longer in a state of perfect adaptation to their surroundings.
There is no longer a necessary correspondence and correlation between organism and habitat, no longer necessary that rhythmical (almost preëstablished) harmony between species and environment. This need only exist so far as is necessary to render the life of the species possible. Beyond this the greatest inharmony and inadaptation may be conceived to reign in Nature. Each plant may be regarded as a reservoir of vital force, as containing within it a potential energy far beyond and wholly out of consonance with the contracted conditions imposed upon it by its environment, and by which it is compelled to possess the comparatively imperfect organization with which we find it endowed. Each individual is where it is, and what it is, by reason of the combined forces which hedge it in and determine its very form. Each species is the perpetual and inexorable antagonist of every other. The "struggle" is not alone "for existence," it is also for place. In the plant races, as in the human, there is a recognized hierarchy, the laws of which are as yet to a great extent involved in mystery. But the first principle, as in the rest of Nature, is force. Each one encroaches with all the power of vegetal growth upon its neighbors. This pressure is enormous. Who shall calculate this subtilest of molecular forces? Yet there is no displacement, no motion. So thoroughly has every nook and chink been filled that there is no room for motion. Like the all-pervading circumambient air, its power is not felt so long as no vacuum is produced. Each organism has long since reached the limit of its power to extend its dominion. The plant grows up from the germ to maturity under a constant surveillance, and every attempt to overstep its fixed limits is instantly checked. It stands in its fixed position, locked in the embrace of forces which permit it neither to advance nor retreat.
Such is the state of equilibrium which is always and necessarily reached in a state of Nature, and in which man first finds each newly-discovered flora. But let these statical conditions be once changed,
