Watch the wormwood. See how the raindrops quiver for an instant on the tips of the pinnate leaves, then follow one another in a mad chase down the groove that traverses the center of each leaf. Notice that the leaf itself rises from three ridges on the stem of the plant, and that between these ridges lie shallow grooves down which the raindrops run to the plant’s root. Now, we can tell from these signs what sort of a root the wormwood has. I never pulled one of the plants, but I am sure that if we were to do so we should find it to have a main tap-root, with no branches. All such plants have leaves pointing upwards, and grooved stems, admirably adapted to bring water to the thirsty roots. The beets and the radishes afford us capital examples of this provision
This alfileria has another arrangement of leaf, for this same purpose. It is a widely spreading forage-plant, with an absurdly small root. It needs a great deal of moisture, and so its stems are thickly set with soft, fuzzy hairs, that catch the water and convey it to the root
Growing all along the bank is the little chickweed, with its tiny white star of a blossom. If it were not so common we should wax enthusiastic over its beauty, and seek it for our garden borders. It has a running, thread-like root, which receives the raindrops caught by the stem in a single row of tiny hairs along its lower side, and sprinkled gently down.
When a plant has a spreading root such as the willow, yonder, sends down, the leaves spread outward and downward, from base to tip, letting their gathered moisture down upon it. When the plant grows under water its leaves are long and thread-like; for the supply of carbon is limited, and they divide minutely, that the greatest possible surface may be exposed to absorb it. If the stem grows until the leaves reach the surface of the water they broaden and spread out, for here they get an abundant food supply which they may freely appropriate, as none of it need be diverted to build up a supporting stem. The water affords the leaves ample support