This clothing of the earth and the cleansing of the air are the tasks the giant rushes helped to perform for the young world. During the process the rank gases of the atmosphere were gradually stored up within their great stems. Liberated, now, in our grates and retorts they give us heat and light. Then, the atmosphere becoming purer, the earth cooled and life sustaining, new growths appeared. All the conditions were improved, but the improvement meant death to the big rush. It was starving. It could not find food in the thin air. Its roots could not suck up enough moisture to sustain life. It became smaller and smaller. Flowers and seeds it had never borne. It now gave up its leaves. Between every two whorls of branches on the scouring-rush we find a little brown, toothed sheath encircling the stem. In the days of the plants’ prosperity each of these teeth was a leaf, but now the rush can maintain no such extravagance as leaves, so there remain only these poor survivals. The stem is hollow, and is divided, between the whorls of branches, into closed sections, orjoints. It has also an outer ring of hollow tubes, through which moisture is drawn up from the soil, to feed the branches. The rush is a little higher order of creation than the fern, but it is a cryptogram; that is, a plant never bearing true seeds, but propagating by spores
And so, fallen upon hard lines, chilled, stunted by the cold, but having a brief span of life when the spring rains have made the earth wet and warm, and before the summer heat has come to wither it, we have our scouring-rush only a few inches high.
☘