This section is from the book "The Gardener's Monthly And Horticulturist V21", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
It is not always the person who has the largest experience in any particular branch of industry, that is the closest observer and possesses the most knowledge of it in every particular. In the cultivation of plants, Mr. Darwin's experience has been but limited when compared with many; but there are few, if any, who know more about the uses and workings of the different organs of plants at the present day than he. There are but very few I think, who following the details of his experiments with the feeding of the different plants examined by him, but will admit that the leaves of plants do something more than merely evaporate moisture.
The experiments also made by Professor Balfour, Edinburgh, assisted by my old friend and fellow laborer, Mr. Lindsay, clearly showed that plants fed through their leaves did increase in weight over such as were only fed through the roots. These experiments were published in the Gardener's Chronicle. Every one knows, who has paid any attention to the study of vegetable physiology, that plant food, before it can be absorbed by either roots or leaves, has to undergo a chemical change; and this change cannot be produced without moisture. A plant, be it ever so great a feeder at the roots of nitrogeneous matter, will not absorb any of it if there is not sufficient moisture to produce the necessary change. Leaves cannot absorb any kind of nourishing food more than roots, without sufficient moisture to bring it into a condition suitable for being absorbed through the organs of the leaves. Mr. Henderson's example of the plants in the neighborhood of the bone manufactories not being benefitted, is not very suitable for the support of the theory he wishes to support; the gases passing off from those factories are not in a suitable condition to be absorbed by the leaves.
Nor would the plants be benefited by the roots coming in contact with it under the same condition.
Mr. Henderson's experience in horticultural work has extended over more years than I have been with mother earth; but I think he must surely have written his last article for the Monthly without much study, when he questions the matter of plants absorbing moisture, and that moist air acts only as a negative benefit; if this were the case, a plant once wilted could not be recuperated by the application of moisture to the leaves; that if it acted only as a negative, the plant would remain the same when moistened on the foliage or brought into a moist atmosphere. Now Mr. H. knows as well as I do that geranium cuttings, for instance, if allowed to wilt, (so long as the organs of the leaves are not destroyed,) then placed in a moist atmosphere will recuperate, and the leaves and stems regain their former plumpness, and get heavier than before being placed in the moist atmosphere. Now I would like to ask Mr. H., if the moisture was not absorbed through the leaves or stems, how was it absorbed, there being no roots ?
I have kept several of the Bilbergias in a moist atmosphere without any roots, and they have grown considerably. Now if they have not fed through their leaves how were they fed? Please try some of them Mr. Henderson, and I think you will come to the conclusion that there are plants which can be nourished for a good while, although the roots are gone.