Physiologie. 425 



has been able to correct the readings of any experiment 1) for 

 changes in the relative humidity of the air, 2) for the direct effect 

 of light on transpiration apart from its effect on the stomata. By 

 means of these and other corrections, a comparison is made be- 

 tween the course of transpiration (as measured directly by weighing, 

 or indirectly by the porometer) and the aperture of the stomata (as 

 measured by the square roots of the readings of the porometer 

 affixed to a control plant under identical conditions). 



The results are expressed both numerically and graphically in 

 a number of cases, and in spite of individual variations. a very 

 close correspondence is shewn between transpiration under different 

 conditions and the behaviour of the stomata. This points to a cau- 

 sal connection between the amount of transpiration and the size of 

 the stomatal apertures; a conclusion opposed to that of Lloyd and 

 some other American botanists who however had less accurate 

 means of investigating the behaviour of the stomata. 



E. M. Delf (Cambridge). 



Delf, E, M., Studies of Protoplasmic Permeabilitj'- by 

 Measurement ofRate ofShrinkage ofTurgid Tissues. 

 1. The Influence ofTemperature on the Permeability 

 of Protoplasm to Water. (Ann. Bot. XXX. p. 283-310. 1016.) 



In this paper the author describes a method by which the 

 shrinkage of Strips of tissue freely supplied with a plasmolysing 

 Solution can be followed optically. In order to find the effect of 

 temperature on the permeability of the protoplasm to water, the 

 Strips of tissue were supplied with Solutions flowing at constant 

 temperatures varying from 5° to 43° C. It was found that it was 

 necessary to employ verj^ weak Solutions in order to follow the 

 contractions successfully at high temperatures. The shrinkage was 

 probably entirely confined to that caused by falling turgor, no Se- 

 paration of the protoplast from the waDs of the cells taking place. 

 A number of curves shewing the course of plasmolysis at the dif- 

 ferent temperatures were obtained, and a coniinuously increasing 

 rate of shrinkage with rise of temperature was clearly seen. In 

 order to estimate the effect of temperature in accelerating the rate 

 of shrinkage, the values of the tangents of these curves at cor- 

 responding points were com.pared. From these values temperature 

 coefficients were calculated which, in the case of onion leaves, 

 varied from 1.4 (5°— 15° C) to 3.0 (30°— 40° C). This is opposed to 

 the conclusions of van Rj^sselberghe, who could not, by his 

 method, detect any appreciable temperature effect above 20"^ C. 



E. M. Delf. 



Dixon, H. K. and E. S. Marshall. A quantitative Exami- 

 nation of the Elements in the Wood ofTrees in rela- 

 tion to the supposed functionoftheCellsintheAscent 

 of Sap. (Sc. Proc. Roy. Soc. Dubl. XIV. N. S. NO 29. 1915.) 



The authors describe experiments to fest the theory of Janse 

 that the medullary ray cells of the wood bring about the raising of 

 the sap by secreting water from below upwards into the vessels 

 and tracheids on which they abut, this secretion being so rapid 

 that it can both supply the transpiration stream and compensate 

 for the leakage downwards due to the permeability of the wood 

 to water. 



