Page:Philosophical Transactions - Volume 095.djvu/113

Rh the true S^ of Trees is deposited during Winter. 99

existence of vegetable circulation, which is denied by so many eminent naturalists. I have not, however, found in their writings a single fact to disprove its existence, nor any great weight in thdr arguments, except those drawn from two important errors in the admirable works of Hales and Du Hamel, which I have noticed in a former memoir. I shall therefore proceed to point out the channels^ through which I conceive the circulating fluids to pass.

When a aeed is deposited in the ground, or otherwise exposed to a proper degree of heat and moisture, and exposure to air, water is absorbed by the cotyledons and the young radicle or root is emitted. At this period, and in every subsequent stage of the growth of the root, it increases in length by the addition of new parts to its apex, or point, and not by any general dis- tension of its vessels and fibres ; and the experiments of Bonnet and Du Hamel leave little grounds of doubt^ but that the new matter which is added to the point of the root descends from the cotyledons. The first motion therefore of the fluids in plants is downwards, towards the point of the root; and the vessels which appear to carry them, are of the same kind with those which are subsequently found in the bark, where I have, on a former occasion, endeavoured to prove that they execute the same oflice.

In the last spring I examined almost every day the progressive changes which take place in the radicle emitted by the horse ches- nut : I found it, at its first existence, and until it was some weeks old, to be incapable of absorbing coloured infusions, when its point was taken off, and i was totally unable to discover any albumous tubes, through which the sap absorbed from the ground, in the subsequent growth of the tree, ascends: but

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