. Experiments with plants. Botany. ffOW PLANTS ARD INFLUENCED 345. as often happens, some of them are directly exposed to the sun while others are continuously shaded. Figs. 128 and 130 show two branches from the same plant: the one shown in Fig. 128 was well illuminated, while the one shown in Fig. 130 was shaded: there is a corre- sponding difference ii; the size of the leaves. Fig. 199 shows the appear- ance of sections of sun- and shade- leaves of the Prickly Lettuce and Fig. 200 of sun- and shade-leaves of the Beech. Especially noticeable in the "sun-leaf" are the longer palisad
. Experiments with plants. Botany. ffOW PLANTS ARD INFLUENCED 345. as often happens, some of them are directly exposed to the sun while others are continuously shaded. Figs. 128 and 130 show two branches from the same plant: the one shown in Fig. 128 was well illuminated, while the one shown in Fig. 130 was shaded: there is a corre- sponding difference ii; the size of the leaves. Fig. 199 shows the appear- ance of sections of sun- and shade- leaves of the Prickly Lettuce and Fig. 200 of sun- and shade-leaves of the Beech. Especially noticeable in the "sun-leaf" are the longer palisade cells, the smaller air-spaces, the greater thickness of the leaf, and thicker cuticle or outer wall of the epidermal cells ; the number of stomata is also smaller. These effects are due partly to the light itself and partly to the dryness (or excessive evapo- ration) caused by the light, heat and wind. Leaves arrange themselves with reference to the direction of the liyht, and many follow the sun during the day (see page 217). Some plants, inhabitants of dry countries, place their leaves in a vertical position, thus avoiding the full effect of the light (see page 200. Beech leaves seen in cross-section: (a) sun leaf, (6) shade 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 Osterhout, Winthrop John Van Leuven, 1871-. New York, The Macmillan company; London, Macmillan & co. , ltd.
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