62 
Knight.— On the Use of the 
The results of this series of experiments show that the treatment 
to which a leaf is subjected in affixing a chamber produces a definite 
stimulation of the stomata, causing them to close to a large extent. 
Recovery from the shock is fairly rapid, taking place in two hours or so, 
and is apparently complete, since it is found that a chamber can be left 
attached to a leaf for days, and readings may be taken daily, whilst the 
stomata still respond to light and darkness, and the leaf is not obviously 
injured. 
A second method was also adopted in the attempt to discover the 
effect upon stomata of shock. Two or more chambers were attached to 
Fig. 3. Effect upon the stomata of fixing a porometer chamber. Eucharis Masteri. 
different leaves of a plant, and when the curves of stomatal aperture 
had attained a regular form, one of the leaves under observation was 
tapped lightly several times with a pencil, or was shaken, and the effect 
upon the stomata was noted in the succeeding readings. It is naturally 
somewhat difficult to standardize tapping or shaking, and it was there- 
fore impossible to treat each leaf similarly. It is possible that this 
accounts for the variety of results obtained. 
Begonia showed no effect at all, the curves of stomatal aperture having 
similar forms whether the leaf was tapped or not. Ficus elastica showed 
no change in two cases, but in a third there was a tendency for the 
stomata to close as a result of tapping. Eucharis Mastersi fairly con- 
sistently closed its stomata, temporarily, in response to tapping. With 
all three plants several experiments showed slight effects which might 
be due to merely experimental error. 
