This section is from the book "The Gardener's Monthly And Horticulturist V18", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
Prof. Karl Koch says in Gardeners' Chronicle: "Among practical gardeners and pomologists not only does this error respecting a rising crude sap or raw food prevail, but many of the current notions as to the real nutritive substances are equally at fault; more particularly that with regard to the direction of assimilated sap, which goes wherever it is needed - that is to say, where it can nourish, as a rule and for the greater part upwards, and in a less degree downwards. In the first place, nobody appears to have attempted to answer the question, When do the leaves become active or begin to assimilate the nutritive substances, the carbon-hydrates? Nor, so far as I know, has it been taken up from a scientific standpoint. As the leaves are already green when they unfold, it has been tacitly admitted that assimilation commences then. But such is by no means the case. The leaves only become active after the shoot has attained its full development. Until this point is reached, the leaves themselves, as well as the axis of the shoot, need nourishment, in order to enable them to reach their natural size, and finally fit them for the work of assimilation."
[The writer of this can confirm Professor Koch's views. In experimenting years ago, he would pick off the leaves of the pushing young branches of Ashes, Horse-Chestnuts, and Maples, as fast as they could be discerned. Nevertheless the shoots would become wood to a considerable portion of the whole length. The material for the organization must have been partly stored up the previous year, and partly drawn from other parts of the plant. - Ed. G. M.]