1904] DARWIN: MOVEMENTS OF STOMATA eee | 
ning through the wires, the bulbs are warmer, by roughly 2°, than 
the surrounding air. Thus the leaf under experiment is not 
in strictly natural conditions, being constantly warmed; in spite 
of the artificially increased transpiration‘ due to this condition, 
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Fic, 1.—See Experiment 83 B, p. 84- 
the leaf behaves normally in showing a marked rise in tem- 
perature as the stomata shut. Nor does the warming of the leaf, 
4 By the use of the horn hygroscope it is possible to show that the part of a leaf 
in contact with the recorder bulbs transpires more than the unheated parts of the 
Same leaf, e following are readings taken on a tulip leaf, February 22, 1901, B 
being the transpiration of the part of the leaf in contact with the bulbs, N of the nor- 
mal parts of the lea 
P.M. N 
4:53 : - - - - : 30 
167.43 «> * ~ . = - - 23 30 
So 
