The ordinary feeding of plants may, lastly, be cited, by way of showing how marvellously intricate must be the conditions which operate to produce differences in habits, sometimes amounting almost to special likings on the part of vegetable units for one kind of food, and equally special dislikes to other foods. The farmer knowing the preference for certain food-elements by certain plants, requires to ‘rotate’ his crops, to avoid injurious exhaustion of his soils. For instance, buckwheat will not flourish unless potassium is supplied to it. The chloride of potassium, and next to it the nitrate, are the minerals preferred by this plant. Still more extraordinary is the preference exhibited by one of the violet tribe (Viola calaminaria), which will only grow in soils that contain zinc. Here, the effects of habit are seen in a singularly clear fashion; for there seems every reason to assume that the partiality for a by no means common element in soils, has been an acquired, and not an original taste of the plants which exhibit it. The botanist thus becomes aware of the existence of a ‘taste,’ or ‘selective power’ as it is termed, in the plant-world, influencing their food, and, as a matter of logic, affecting also their structure, functions, and entire existence. It has been found that the pea and bean tribe (Leguminosæ) specially desire lime, amongst their requirements. Potatoes exhibit a special partiality for potash; and turnips share this taste. Plants in which the seed assumes a high importance, as in most of our cereals, on the other hand, demand phosphoric acid; and certain plants, such as wheat, will withdraw large quantities of silica or flint from the soil. Iodine is found characteristically in seaweeds, and the element in question is obtained from the kelp produced by burning marine plants.
No better commentary on the life and habits of plants in respect of their food-tastes can be given than in the words of an eminent physiologist, who, speaking of the food of the corn-plant, says: ‘Without siliceous (or flinty) earth, that plant cannot acquire sufficient strength to sustain itself erect, but forms a creeping stem, feeble and pale; without calcareous earth (or lime), it dies even before the appearance of the second leaf; without soda and without potash, it never attains a greater height than between four and five inches; without phosphorus, though growing straight and regularly formed, it remains feeble and does not bear fruit; when iron is present in the soil, it gives that deep green tint so familiar to us and grows rapidly robust; without manganese, it develops in a stunted manner and produces few flowers.’ After the revelations of chemistry concerning the habits and tastes of plants and the bearing of proper food on their growth, it is not to be wondered at that scientific agriculture should be regarded as the only solution of many of the present-day difficulties of the farmer.
IN ALL SHADES.
CHAPTER X.
For a second, nobody answered a word; this quiet declaration of an honest self-sacrifice took them all, even Nora, so utterly by surprise. Then Edward murmured musingly: ‘And it was for this that you gave up the prospect of living at Cambridge, and composing symphonies in Trinity gardens!’
The mulatto smiled a deprecating smile. ‘Oh,’ he cried timidly, ‘you mustn’t say that. I didn’t want to make out I was going to do anything so very grand or so very heroic. Of course, a man must satisfy himself he’s doing something to justify his existence in the world; and much as I love music, I hardly feel as though playing the violin were in itself a sufficient end for a man to live for. Though I must confess I should very much like to stop in England and be a composer. I’ve composed one or two little pieces already for the violin, that have been played with some success at public concerts. Sarasate played a small thing of mine last winter at a festival in Vienna. But then, besides, my father and friends live in Trinidad, and I feel that that’s the place where my work in life is really cut out for me.’
‘And your second great passion?’ Marian inquired. ‘You said you had a second great passion. What is it, I wonder?—Oh, of course, I see—your profession.’
(‘How could she be so stupid!’ Nora thought to herself. ‘What a silly girl! I’m afraid of my life now, the wretched man’ll try to say something pretty.’)
‘O no; not my profession,’ Dr Whitaker answered, smiling. ‘It’s a noble profession, of course—the noblest and grandest, almost, of all the professions—assuaging and alleviating human suffering; but one looks upon it, for all that, rather as a duty than as a passion. Besides, there’s one thing greater even than the alleviation of human suffering, greater than art with all its allurements, greater than anything else that a man can interest himself in—though I know most people don’t think so—and that’s science—the knowledge of our relations with the universe, and still more of the universe’s relations with its various parts.—No, Mrs Hawthorn; my second absorbing passion, next to music, and higher than music, is one that I’m sure ladies won’t sympathise with—it’s only botany.’
‘Goodness gracious!’ Nora cried, surprised into speech. ‘I thought botany was nothing but the most dreadfully hard words, all about nothing on earth that anybody cared for!’