. Hydration and growth. Growth (Plants); Plants. Some Hydration Reactions and Growth. 147 12 m. 5 10 / / ./I / X45 I9"C. 14-d, i -+-â - -T 1â 15 T / / 25'C. 5 15 25 / / ^ // L. 1/ (/ |l8°C. / â '"â 1 1 manner described, and a portion of the record is given in figure 35. As may be seen, the period of shrinkage, which begins about the same time in the older leaf, continues for a shorter period, on some days not more than 2 hours, and enlargement sets in in mid- afternoon. The thickness on each successive morning was greater than at the same time on the preceding day
. Hydration and growth. Growth (Plants); Plants. Some Hydration Reactions and Growth. 147 12 m. 5 10 / / ./I / X45 I9"C. 14-d, i -+-â - -T 1â 15 T / / 25'C. 5 15 25 / / ^ // L. 1/ (/ |l8°C. / â '"â 1 1 manner described, and a portion of the record is given in figure 35. As may be seen, the period of shrinkage, which begins about the same time in the older leaf, continues for a shorter period, on some days not more than 2 hours, and enlargement sets in in mid- afternoon. The thickness on each successive morning was greater than at the same time on the preceding day, demonstrating that actual growth was in progress. Two series of measurements were nowim- dertaken to secure new records of the elonga- tion of leaves which had reached about half the final length and of others stiU younger. Such a pair of young leaves, with their surfaces still appressed in an erect position, were brought into bearing on an auxograph lever in a sunny place in a glass-house. The length of the exposed portion was about 25 mm. and their thickness was not over mm. at the begiiming of the tests. Here, as in previous preparations, it was foimd that whatever the causes of the stoppage of growth and of shrinkage might be, they were not effective in producing an actual cessation of elongation, which in these young leaves continued through- out the 24 hours of the day variously respon- sive to alterations in temperature (fig. 36).^ Another pair which were about to spread by the growth of the bud ensheathed between their bases were attached to the auxograph and set in a place where they would be shielded from the direct rays of the sun. Preparations of all three stages increased in length and thickness FiQ. 34.âUpper part of fig- ure is an auxographic rec- ord of variations in thick- ness of leaf of Mesembry- anthemum on a cloudy day with but little change in temperature, as taken by a mercurial thermom- eter from a similar leaf. Upward course of line de- not
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectplants, bookyear1920
