. Carnegie Institution di Washington la pubblicazione. Alcune reazioni di idratazione e di crescita. 147 5 10 15 12p.m. m. J2pm 7 / / / / X45 /I9°C. I4°(J(. / Z 7^ T / 25°C. 12 p.m.. modo descritto, e una porzione del record è data in figura 35. Come può essere visto, il periodo di contrazione che inizia circa lo stesso tempo nei vecchi leaf e continua per un periodo più breve, su alcuni giorni e non più di 2 ore e l'ampliamento set in a metà pomeriggio. Lo spessore su ogni mattina era maggiore rispetto allo stesso tempo il giorno precedente, dimostrando che la crescita effettiva era in corso. Due serie di
2208 x 1132 px | 37,4 x 19,2 cm | 14,7 x 7,5 inches | 150dpi
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. Carnegie Institution of Washington publication. Some Hydration Reactions and Growth. 147 5 10 15 12p.m. m. J2pm 7 / / / X45 /I9°C. I4°(J(. / z 7^ T / 25°C. 12 p.m.. 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 now un- dertaken to secure new records of the elonga- tion of leaves which had reached about half the final length and of others still younger. Such a pair of young leaves, with their surf aces 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 0.5 mm. at the beginning of the tests. Here, as in previous preparations, it was found 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).1 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 FIG. 34.—Upper 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- notes increase. X45. Lower figure is an auxo- graphic tracing of sa
