And so of the alpine firs, grasses, harebells, lichens, mosses, etc. Their seeds have not been scattered, by any known agencies, over intervening regions, for thousands of miles or more, in order to find lodgment on these lofty mountain cones; but, conditions being the same, the same vegetable growths appear. This is nature's method of propagating "vital units" and diversifying plant-life--geographical conditions everywhere determining the proper distribution. But if nature is so prolific of vital resources, in the propagation of plant-life, what need has she of natural seeds? We anticipate this inquiry only to answer it; for we recognize it as a legitimate one in this connection. Our answer is that the seeds are given for the use of man, that he may control and utilize vegetation, and not have to depend on more or less uncertain conditions. Agricultural chemistry must be carried to a much higher degree of perfection than it is likely to reach in the next ten centuries at least, to determine whether any particular plat of ground has been chemically balanced for the growth of wheat, to the exclusion of other cereal crops. Besides, the process of soil-balancing might be altogether too expensive to be indulged in by judicious husbandry. These chemical conditions admit of too many possible failures, in balancing even the smallest patch of ground, to justify experiments in the direction named. Seeds also subserve the important subsidiary purpose of supplying food for many birds and animals, more or less useful to man. But chemistry has its limits as to usefulness in all human laboratories. As man's wisdom is limited, so is his power over the elementary forces of nature confined to very narrow boundaries. It is given to him to search out many inventions, and to pry, thus far and no farther, into the secrets of nature, or, more properly speaking, into the secrets of God. There is no doubt that if our chemico-molecular theorists respecting life-phenomena, could produce, in their laboratories, the exact inter-uterine plasma, or plasmic conditions, of an animal--any animal, in fact--and continue these conditions during the proper period of gestation, they _might_ produce life _de novo_.[13] But the most daring physicist would stand aghast at the bare proposal of such an experiment. Neither his knowledge of chemistry, nor the present uncertain value attaching to "molecular machinery," would justify him, for a moment, in entering upon such a purely tentative and empirical an undertaking.