But how about the juice, the sap, the qualities of the soil, the manure required? is the incredulous cry of Other People. What is the use of the roots, and especially of the rootlets, if they are not the mouths and supply-tubes of the plants? Well, I plainly perceive I can get 'no forrarder,' like the farmer with his claret, till I've answered that question, provisionally at least; so I will say here at once, without further ado--the plant requires drink as well as food, and the roots are the mouths that supply it with water. They also suck up a few other things as well, which are necessary indeed, but far from forming the bulk of the nutriment. Many plants, however, don't need any roots at all, while none can get on without leaves as mouths and stomachs. That is to say, no true plantlike plants, for some parasitic plants are practically, to all intents and purposes, animals. To put it briefly, every plant has one set of aerial mouths to suck in carbon, and many plants have another set of subterranean mouths as well, to suck up water and mineral constituents. Have you ever grown mustard and cress in the window on a piece of flannel? If so, that's a capital practical example of the comparative unimportance of soil, except as a means of supplying moisture. You put your flannel in a soup-plate by the dining-room window; you keep it well wet, and you lay the seeds of the cress on top of it. The young plants, being supplied with water by their roots, and with carbon by the air around, have all the little they need below, and grow and thrive in these conditions wonderfully. But if you were to cover them up with an air-tight glass case, so as to exclude fresh air, they'd shrivel up at once for want of carbon, which is their solid food, as water is their liquid.