. Rustic sounds and other studies in literature and natural history. Galton, Francis, Sir, 1822-1911; Austen, Jane, 1775-1817; Hales, Stephen, 1677-1761; Darwin, George Howard, Sir, 1845-1912; Natural history. PICTURESQUE EXPERIMENTS 213 Porometer. Its essential part is shown in Fig. 7. It consists of a funnel-shaped tube, having a broad flange, which is cemented on to the stomata-bearing surface of a leaf. The leaf is represented by the obliquely shaded object and is enormously magni- fied. To the upper orifice of the funnel is fixed a rubber tube, and by means of it steady suction can be sup
. Rustic sounds and other studies in literature and natural history. Galton, Francis, Sir, 1822-1911; Austen, Jane, 1775-1817; Hales, Stephen, 1677-1761; Darwin, George Howard, Sir, 1845-1912; Natural history. PICTURESQUE EXPERIMENTS 213 Porometer. Its essential part is shown in Fig. 7. It consists of a funnel-shaped tube, having a broad flange, which is cemented on to the stomata-bearing surface of a leaf. The leaf is represented by the obliquely shaded object and is enormously magni- fied. To the upper orifice of the funnel is fixed a rubber tube, and by means of it steady suction can be supplied. The result is that a current of air is drawn through the stomata into the leaf, and. jO*M 11 ?2 1 2 Fig. 8. Curve of Porometer readings in light and darkness (black). then out of the leaf into the cavity of the poro- meter. The rate of this current is an index of the degree to which the stomata are open. With this apparatus a number of interesting points can be determined. Fig. 8 shows the effect of alternate periods of light and darkness. The fall of the curve represents. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Darwin, Francis, Sir, 1848-1925. London, Murray
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