286 ‘REV. G. HENSLOW ON TRANSPIRATION 
I. Transpiration as a Function of Living Protoplasm; II. Tran- 
spiration, and III. Evaporation, in a Saturated Atmosphere. 
By the Rev. G. Hewstow, F.L.S. 
[Read 2nd June, 1887.] 
I. TRANSPIRATION AS A FUNCTION OF Livina PROTOPLASM. 
Introductory.—That green leaves and other parts of plants tran- 
spire vapour of water from their surfaces has long been known; 
that this transpiration is greater by day than at night, and that 
it is augmented by heat, has been equally well ascertained ; that 
it is chiefly induced by the absorption of the red and violet, and 
to a less extent by some other of the rays of the solar spectrum, 
when white light impinges upon organs containing chlorophyll, 
bas been satisfactorily demonstrated. That it is not, however, 
strictly speaking a function of chlorophyll, per se, but rather one 
of living protoplasm generally, whether green or colourless, 
seemed to require confirmation, and is one of the results of the 
experiments herein to be described. 
My object has been to find out, if possible, how far transpira- 
' tion is effected by light, both white as well as coloured, and 
by temperature without the aid of chlorophyll; and if under 
this condition it could be compared with the purely physical 
property of evaporation which takes place from all moist sub- 
stances. 
MM. Bonnier and Mangin, in their experiments upon the 
respiration and transpiration of Fungi, arrived at the following 
conclusions * :— 
“1. La transpiration est augmentée par l'élévation de la tem- 
pérature. 
“2. La transpiration diminue quand l'état hygrométrique de 
l'air augmente. 
“3. La lumiére diffuse augmente la transpiration des Cham- 
pignons." 
With reference to the differences between Transpiration and 
Evaporation, M. Leclerc has arrived at the following results f :— 
“1°. La transpiration est indépendante de la lumiére. 
* Ann. des Sci. Nat. 6 sér. tome xvii. p. 302. 
t Ibid. 6 sér. tome xvi. p. 274. 
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