. Carnegie Institution of Washington publication. SOIL MOISTURE AND TO EVAPORATION. 63 11 , August 19. The plant began to wilt at the last-named hour. The total leaf area was sq. cm. During the entire period the plant transpired at the average rate of grams per hour, or gram per unit leaf surface. Owing to the short period no curve was constructed for this plant. Experiment XV. — This test was performed with three seedling squash plants (Cucurbita pepo), each having two leaves besides the cotyledons. The soil about them had been kept moist since germi- nation and they h
. Carnegie Institution of Washington publication. SOIL MOISTURE AND TO EVAPORATION. 63 11 , August 19. The plant began to wilt at the last-named hour. The total leaf area was sq. cm. During the entire period the plant transpired at the average rate of grams per hour, or gram per unit leaf surface. Owing to the short period no curve was constructed for this plant. Experiment XV. — This test was performed with three seedling squash plants (Cucurbita pepo), each having two leaves besides the cotyledons. The soil about them had been kept moist since germi- nation and they had grown with exceedingly great rapidity. The three plants together possessed a total leaf surf ace of sq. cm. They were sealed August 16 at 12"30m , and had begun to wilt at 3"30m During this period of three hours they trans- pired at the rate of grams per hour, or gram per square centimeter of leaf surface. For this period of three hours their rate of relative transpiration was GENERALIZATIONS FROM THE EXPERIMENTS. It appears from the data just presented that Euphorbia, Trib- ulus, Allionia, and Boerhavia all show a periodic fluctuation in their relative transpiration. The highest relative transpiration ob- served was (Experiment VIII) and the lowest was (Experiment IV). They all have some form of regulative response whereby transpiration begins to be checked between 6h30m and 1 , the check being generally removed between 6 and 8 It also appears that in all three forms stomatal or some internal foliar responses probably play the most important role in this regulation of water loss, these being aided perhaps by nyctitropic movements in the first two forms mentioned. As far as the limited data at hand can be. FIG. 16.—Curve of relative transpiration for three plants of Boerhavia, August 16-17, Please note that these images are extracted from scanned page images that may have been digitally enhanced fo
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