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Work of the Leaves — Part 2 — Part 2

When daylight is gone, the exchange of these two gases ceases. There is no excess of oxygen nor demand for carbon dioxide until business begins in the morning. But now a process is detected that the day's activities had obscured.

The living tree breathes--inhales oxygen and exhales carbonicacid gas. Because the leaves exercise the function of respiration, they may properly be called the lungs of trees. For the respiration of animals differs in no essential from that of plants.

The bulk of the work of the leaves is accomplished before midsummer. They are damaged by whipping in the wind, by the ravages of fungi and insects of many kinds. Soot and dust clog the stomates. Mineral deposits cumber the working cells. Finally they become sere and russet or "die like the dolphin," passing in all the splendour of sunset skies to oblivion on the leaf mould under the trees.