IN THE MOTOR ORGANS OP LEAVES. 



13 



pinnae began to show rotation and depression, whilst the 



ned the fully 



developed diurnal position unaltered. The fact that boiling the tissues in such cases 

 leaves their conducting power for water unimpaired, whilst reducing their retentive power, 

 could hardly be more clearly demonstrated than it is in the results of this experiment 

 by the phenomena of exudation in the boiled areas and full expansion of the distal intact 

 ones whilst the leaf remained in a moist atmosphere, and of disappearance of exudation 

 and partial assumption of the nocturnal position by the same pinna? when the leaf was 

 exposed to free evaporative loss. On the following day the level of the water in the 

 bottle had sunk so much that only the tip of the petiole remained immersed. The boiled 

 portions of the leaf were dry and brown, the others were green and turbid, but somewhat 

 inclined towards the nocturnal position. The leaf was now returned to a hermetically 

 closed chamber, and on the following day exudation had reappeared on tho boiled portion 

 of the rachis and the intact pinna) were once more in a condition of full expansion. 



Experiment V. — Two leaves of Cassia sumatrana were taken, the one, «, having seven 

 pairs of pinnae, the other, which was somewhat larger, only six and a half pairs. The 

 third pair of pinna? and the corresponding portion of the rachis of a were immersed in 

 boiling water, the treatment causing almost immediate browning and flaccidity of the 

 immersed tissues, and temporary drooping, with more or less assumption of the nocturnal 

 position in the pinnae beyond the point of immersion. Tho bases of the petioles of 1 -th 

 leaves were now freshly divided under water and then securely luted into water-bottles, 

 the levels of the water in the latter being at the same time accurately marked. The 

 leaves stood side by side in the open laboratory until the following day, when both 

 were found to be alike turgid, save the boiled portions of a, which, as usual with 

 exposed portions of tissue after similar treatment, were brown, dry, and drooping. The 

 amount of water which had been absorbed during the interval in both cases was ( 6c.e. 



Experiment VI. — A large leaf of Cassia alata was taken, and all but the five distal 

 pairs of pinnae were cut off. The lower part of the petiole was then plunged into boiling 

 water for half a minute, and, its extremity having been cut off subaqueously, was luted 

 into a water-bottle. The apparatus was then set in a sealed chamber containing a vessel 

 of strong sulphuric acid. The level of the water in the bottle began at once to descend 

 visibly. On the following day that part of the boiled portion of the petiole which was 

 above the water was of a brown colour and coated with drops of brown fluid. The 

 pinnae at the same time were fully expanded, turgid, bright green and, as usual when 

 saturated with fluid, studded marginally with drops of clear liquid. The water in the 

 bottle had meantime sunk very considerably. On the two following day3 the pinnae 

 retained their greenness and turgidity, and at the close of the experiment the quantity 

 of water which had been absorbed amounted to Vjc.c. 



Experiment VII. — A large leaf of Cassia alata was taken, the basal pair of pinnae 

 removed, and the lower four and a half inches of the rachis immersed in boiling 

 water for two minutes. The end of the petiole was then freshly cut off under water, 

 and the Jeaf set in an open water-bottle and fixed, so that the lower part only of the 

 boiled portion of the petiole was immersed. Visible depression of the level of the 

 water set in at once, and in the course of two hours a loss of 12c. c. had occurred. 

 On the following morning an additional loss of 3Sc.c. was registered, giving a total 



