. A manual of botany. Botany. EPISTEOPHE AND APOSTROPHE 487 off altogether for a considerable time and other conditions are unfavourable, they collect on the lateral and lower walls. In the illuminated leaf they are found to have partially rotated so as to present their edges instead of their surfaces to the light, and to have collected upon the lateral walls. In the first case the ohloroplasts lie parallel to the surface of the organ ; in the last they are at right angles to the surface. These two conditions are known as epistrophe and apostrophe respectively. "When the conditions of the
. A manual of botany. Botany. EPISTEOPHE AND APOSTROPHE 487 off altogether for a considerable time and other conditions are unfavourable, they collect on the lateral and lower walls. In the illuminated leaf they are found to have partially rotated so as to present their edges instead of their surfaces to the light, and to have collected upon the lateral walls. In the first case the ohloroplasts lie parallel to the surface of the organ ; in the last they are at right angles to the surface. These two conditions are known as epistrophe and apostrophe respectively. "When the conditions of the incidence of the light are altered. Pig. Fig. 1192. Desmodium gyrans. A. Stem with leaves during the day. B. A similar stem with leaves in the nocturnal position, pointing downwards. (After Darwin.) the chloroplasts change their positions accordingly. We see in these phenomena a power of the protoplasm to respond to an increase of illumination in such a way as to protect the plant from injurious consequences. The effect of light upon structure also can be noted in the case of such leaves as are brightly illuminated; the pahsade parenchyma being much more fully developed than in leaves which have grown in the shade. Indeed, the differentiation of the mesophyll into pahsade and spongy parenchyma may be traced to the difference of illumination which the two faces. 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 Green, J. Reynolds (Joseph Reynolds), 1848-1914. London, J. & A. Churchill
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectbotany, bookyear1895
