CHAP. XV. 
IRRITABILITY. 
423 
which there is much ingenious speculation upon the imme- 
diate causes of this singular property. 
That a peculiar kind of irritability does exist in plants, not 
very different from what we remark in animals, has been 
shown in part by the experiments of Marcet already quoted, 
and still more by those of Macaire. 
The former observer proved that narcotic and irritating 
poisons produce an effect upon vegetables altogether analogous 
to that which they produce upon animals. The very valuable 
experiments with gases by Turner and Christison, mentioned 
formerly, lead to the same conclusion. These gentlemen re- 
mark that ‘‘ the phenomena, when compared with what was 
observed in the instances of sulphurous and hydrochloric acid, 
would appear to establish, in relation to vegetable life, a dis- 
tinction among the poisonous gases, nearly equivalent to the 
difference existing between the effect of the irritant and the 
narcotic poisons on animals. The gases which rank as irri- 
tants in relation to animals seem to act locally on vegetables, 
destroying first the parts least plentifully supplied with 
moisture. The narcotic gases, — including under that term 
those that act on the nervous system of animals, — destroy 
vegetable life by attacking it throughout the whole plant at 
once. The former, probably, act by abstracting the moisture 
of the leaves ; the latter, by some unknown influence on 
their vitality. The former seem to have upon vegetables none 
of that sympathetic influence upon general life, which in 
animals follows so remarkably injuries inflicted by local 
irritants.” 
A similar result was arrived at by Macaire, whose experi- 
ments are recorded in the Bihliotheque Universelle, xxxi. 244., 
and which appear of sufficient importance to be detailed at 
length. 
The first plant used was the Berberis vulgaris. The six 
stamina of the flowers of this plant have the property of 
rapidly approaching the pistil, when touched by the point of 
an instrument. The motion occurs at the base of the stamens. 
When cold, the motion is sometimes retarded. When put 
into water or solution of gum, the flowers may be preserved 
many days, possessing their irritability. The petals and 
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