SETZE 
288 REV. G. HENSLOW ON TRANSPIRATION 
he attributes this relaxation to the absence of solar radiations ; 
finally observing :—“ La Transpiration des plantes est un phéno- 
méne complexe qui subit, d’une part les mémes influences physiques 
que l'évaporation de l'eau pure et qui, d'autre part, s'effectuant 
sous l'empire des forces, physiologiques de la vie végétative, 
s'écarte nécessairement de ces lois suivant les besoins de la 
plante. Ce n'est que par des observations de toutes les heures 
et plus souvent répétées encore si c'était possible, qu'on peut 
espérer découvoir les raisons de ces écarts." 
One great objection amongst others to the idea that transpira- 
tionis referable to evaporation, which in turn is regulated by 
temperature and the hygrometric state of the air, is that a living 
leaf loses water more slowly than when it is dead*. I have 
proved this repeatedly in the following manner. Taking a 
variety of leaves and dividing them longitudinally, I suddenly 
killed one half by scalding. I then weighed them, and again at 
short intervals till the two halves of each leaf had dried up and 
lost no more weight. The killed half dried up faster, the loss 
per hour being greater than from the living half. 
As another remarkable difference, it will be seen from the 
tables given below that while living parts of plants can absorb 
vapour at night in a saturated atmosphere, wet cotton-wool never 
does so. 
For further details upon the effects of temperature, and of 
different hours of the day and of month of the year, upon Tran- 
spiration as compared with Evaporation, the reader is referred 
to M. Masure's interesting paper. 
EXPERIMENTS WITH MUSHROOMS. 
The first series of experiments were made with Mushrooms 
transplanted separately from a bed into small pots about two 
inches deep. The latter were entirely enveloped in guttapercha 
sheeting, cotton-wool being wrapped round the stipes to protect 
it from injury, where the sheeting was carefully and somewhat 
tightly fastened, so that no moisture could escape otherwise than 
by transpiration from the plant itself. 
The following table gives the results of observations upon three 
* Dr. Vines also mentions this fact, ‘Phys. of Plants, p. 105. 
REEI 
