Physiologie. 5 



the concentration is directly proportional to the logarithm of the 

 time required to kill practically all the cells. 



4. Evidence that each of the 3 poisons, hydrochloric acid, 

 pyrocatechin and resorcin has a specific action in killing is obtained 

 by showing that a mixture of all three, containing ^j^ oftheamount 

 of each that would have killed alone in ten minutes, does not kill 

 in ten minutes. There is no additive effect. J. J. Blackman. 



Henslow, G., Absorption of Rain and Dew by the green 

 parts of plants. (Journ. roy. hortic. Soc. XXXIV. p. 167 — 173. 



1908.) 



A lecture in which the author reviews the evidence for the 

 absorption of water through the wetted surfaces of leaves and stems. 

 He points out that absorption of water must not be looked for in 

 fully turgid plants but may be considerable when wilted leaves and 

 stems are wetted superficially. 



Experiments are quoted showing the gain of weight when the 

 Upper or the lower surfaces of partly wilted leaves are exposed to 

 spray and dew or floated on water. This varies a good deal with 

 the species as does also the power of a few submerged leaves. to 

 prolong the life of the the rest of a cut shoot which is in air without 

 any other water-supply. J. J. Blackman. 



Smith, A. M., On the internal temperature of leaves in 

 tropical insolation with special reference to the effect 

 of their colour on the temperature; also observations on 

 the Periodicity of the appearance of young coloured 

 leaves of trees growing in Peradeniya Gardens. (Ann. 

 royal bot. Gardens, Peradeniya, IV. p. 229—298. 1909.) 



The first part of this paper consists of observations made in 

 Ceylon on the actual internal temperatures attained by leaves in 

 sun and shade. These observations were made by a fine thermo- 

 junction imbedded in the midrib or mesophyll of the leaf, connected 

 with a portable galvanometer reading to 0.5° C. In still air, when 

 the shade temperature is 25°— 28°C and the insolated black-bulb in- 

 vacuum thermometer rises to 55° — 62° C and the humidity is about 

 700/o leaves of all kinds may rise 12° C to 16° C above the shade 

 thermometer when placed normal to the sun's rays. In the shade 

 these leaves may be from 1.5° C below to 4°C above the temperature 

 of an adjacent thermometer. Arrest of transpiration in the sun, as 

 when two leaves are clamped together with their Stomatic faces 

 inwards causes a further rise of 2°— 3°C. 



The temperature of leaves in the sun is much lowered by a 

 gentle breeze and winds of different velocities may cause the tem- 

 perature to be 2°— 12°C lower than in still air. The thickness of a 

 leaf does not seem to affect the final temperature in the sun though 

 of course it affects the time taken to reach it. 



Special attention was paid to red, yellow and colourless leaves 

 and there is a clear historical account of the literature on the signi- 

 ficance of anthocyan in leaves. Direct experiments support Stahl's 

 theory that a red leaf becomes hotter than a green one. 



The second part of the paper contains observations, made 

 through one year, of the times at which different trees put out new 

 crops of young foliage. Of those species which show marked discon- 



