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Show 292 GERMINATION very small trouble it is, we should never have gone about to cultivate timber in one plant, by the very process whereby we destroy timber in all other plants. Yet we have done and we continue to do that; for, grafting excepted, we breed oaks and peaches in the same ground, and much after t~e same manner. We may make some difference 111 the mould in which they grow ; or we may choose that which we fancy will be the best for each; but we do not even that as observers of nature, at least as very attentive or close observers; for our good soil for oak is that on which we have seen large oaks growing, whether the timber of those oaks happened to be good or bad. Let us return to our acorn and our .e~bryo o~k. That embryo plant, we shall s~ppo~e, I~ JUSt begmning to b~ indepe~dent, ~y w~uch tu_ne It may hav~ stricken Its root SIX or mght mches mto the ground, for the oak remains much longer on the cotyledons· than many other trees, and has also a root and root.J lets ready for action in the earth. The cotyledons do not rise and partially take the for~ and probably perform the functions of leaves, a~ I~ many other plants; so that the action of the a1r IS c~mfi~ed to the risin<:r plumule, and the true leaves which 1t puts. forth. When the acorns are sown ~y nature, t~ey are sown on the surface, not under It. By lookmg back to figure A, on page 93,. it will be seen that the sprout tends dow11:wards, .as 1f. to reach the ground, while the acorn hes on Its s1de upon . the. surface, though even then the little tubercle which. IS ~o become the tree keeps its apex upwards. I~ 1s evident, therefore, that that part of the process 1s naturally done in the air; and, though Reeds are better to have the light excluded during what may be ca~led .tho "fermentative" part of the pr<?cess o~ germmat10n, which is the earliest stage of It; yet m .the case of the acorn, that is over before the shell xs ruptured. The acorn from which the figure was drawn was• OF OAKS. 293 taken from under the earth, not above an inch or an inch and a half indeed, but still under a firm covering, so as to exclude the light from it altogether, and the air nearly so, at least the free action of the air; and, unless by some effort, which it is not easy to see any agent capable of producing, the first leaves must have been formed, and the character of the oak determined, before the light could possibly have had the smallest effect upon it. Now it is very much to be suspected that it is at this early stage that the mischief is done ; and I am the more inclined to that opinion from the fact that the practical men seem to know very little about the process of germination, even in those seeds which they are sowing by thousands, nay, millions, every year,-there is not much, indeed, in the professed writers on vegetable physiology. The agency of light was not understood in the days of Grew and Malpighi ; and though that agency be better understood now, there has not been very much added to the other branch of the science. Besides, the buried acorn does appear to make some sort of effort to come to the surface, and when it i~ there the cotyledon~ acquire a greenish tinge, which they do not acqmre when buried; and that clearly lihows that in their natural state, they give to the food with which they supply the young plant some of that preparation which vegetable matter receives from the action of light. The condition of ·all blanched and etiolated plants, compared with that of the very same species freely exposed to the air, cl~arly .show~ that carbon. and astringency, the very things m which the penshable oak timber is defici. ent, are. among the princ~pal results of the operatiOn of light. These additiOns appear to hinder rather than forward mere growth at the time for an etiolated potato will rise thirty feet in th~ dark whereas it would not rise as many inches if exposed B bQ |
