. Fundamentals of botany. Botany. 138 THE VEGETATIVE PUNCTIONS OF PLANTS in an abnormal manner.^ Under conditions of normal illu- mination (granted, of course, that all other conditions are normal), the physiological processes of the plant are regu- lated in a normal manner; but when the illumination is abnormal, healthy regulation ceases, and the organ be- haves abnormally. This abnormal behavior includes the failure of chlorophyll to develop, and irregularities of growth. With many plants the stems grow abnormally long and slender, suggesting that absence of light favors more rapid growth in
. Fundamentals of botany. Botany. 138 THE VEGETATIVE PUNCTIONS OF PLANTS in an abnormal manner.^ Under conditions of normal illu- mination (granted, of course, that all other conditions are normal), the physiological processes of the plant are regu- lated in a normal manner; but when the illumination is abnormal, healthy regulation ceases, and the organ be- haves abnormally. This abnormal behavior includes the failure of chlorophyll to develop, and irregularities of growth. With many plants the stems grow abnormally long and slender, suggesting that absence of light favors more rapid growth in Fig. g6.—Potted plants of an oxalis showing the position of the leaflets during the day {A) and the night {B)—the so-called "sleep" of plants. (Photo by the author.) 134. Relation of Leaves to Light.—More than all other organs of the plant, the foKage-leaf is developed and ad- justed with reference to illumination. Its form, dimen- sions, and internal structure, and its attitude and posi- tion on the stem are chiefly expressions of the surround- »It is often stated in "popular" writings that stems grown in darkness' "reach for" or "seek" the light. A careful consideration by the student of all that these terms imply, when predicated of a plant, will lead at once to a recognition of their incorrectness, and even of their 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 Gager, C. Stuart (Charles Stuart), 1872-1943. Philadelphia, P. Blakiston's son & co.
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