. Lessons in botany. Botany. 112 BOTANY. the rays of light which fall upon them. Leaves, then, exposed to the brightly lighted sky are, in general, horizontal. This position is taken in direct response to the stimulus of Fig. 91. Sunflower plant removed from darkness, leaves extending under influence of light (diaheliotro- pism). The leaves of plants with a one-sided illumination, as can be seen by trial, are turned with their upper surfaces toward the source of light, or per- pendicular to the incidence of the light rays. In this way light over- comes for the time being the direc- tio
. Lessons in botany. Botany. 112 BOTANY. the rays of light which fall upon them. Leaves, then, exposed to the brightly lighted sky are, in general, horizontal. This position is taken in direct response to the stimulus of Fig. 91. Sunflower plant removed from darkness, leaves extending under influence of light (diaheliotro- pism). The leaves of plants with a one-sided illumination, as can be seen by trial, are turned with their upper surfaces toward the source of light, or per- pendicular to the incidence of the light rays. In this way light over- comes for the time being the direc- tion which growth gives to the leaves. The so-called " sleep" of plants is of course not sleep, though the leaves f '£â 9°- '' nod,'' or hang downward, in many Sunflower plant. Epinastic _,, condition of leaves induced dur- cases. 1 here are many plants in ine the day in darkness. .... which we can note this drooping of the leaves at nightfall, and in order to prove that it is not determined by the time of day we can resort to a well-known experiment to induce this condition during the day. The plant which has been used to illustrate this is the sunflower. Some of these plants, which were grown in a box, when they were. 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 Atkinson, George Francis, 1854-1918. New York, H. Holt and company
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