As root hairs are very much alive and work constantly, they must be provided with air, without which no living thing can exist. And here, again, it seems as though nature, with almost uncanny foresight, had deliberately planned for this requirement of roots. And, in this case, not by interfering with a physical process by an adjustment of plant structure, but by the arrangement of soil particles and the way in which water is found in all soils. Soil particles, even in the most compact clay, do not fill _all_ the space occupied by the soil as a whole. There are tiny air spaces all through the soil, which insures a constant supply of fresh air. That is one reason why gardens are cultivated, to see to it that plenty of fresh air is allowed to permeate the soil. Around the finest soil particles there is always an almost incredibly thin film of water, which is renewed as soon as it is lost by its absorption by the root hairs or by evaporation. This renewal of the water film is itself a mechanical process, called capillarity, best illustrated by putting a few drops of water on a plate and placing on them a lump of sugar. The water will spread all through the lump of sugar in a few seconds and the capillarity that forces it up through the lump is the same as sees to it that the tiny film of water surrounding the finest soil particles is constantly renewed from the lower levels of the soil. Little do we dream, as we walk over the commonest weed, that buried at its roots are these delicate arrangements for securing food and water. Osmosis allowed to act so that the “exchange” of liquids is all to the advantage of the plant, capillarity providing a constant water supply, and the very piling together of the soil so contrived that the life-giving air filters all through it--does it not seem as if all this were, if not a deliberate plan, certainly a more perfect one than mere man could have devised?