PLANTS. 
stalk erects itself, and the flowers rise above the 
surface of the water : in this state they continue till 
four in the afternoon, when the stalk becomes re- 
laxed, and the flowers sink and close. The mo- 
tions of the sensitive plant have been long noticed 
with admiration, as exhibiting the most obvious 
signs of perceptivity. And if we admit such mo- 
tions as criteria of a like power in other beings — to 
\ attribute them in this instance to mere mechanism, 
actuated solely by external impulse, is to deviate 
from the soundest rules of philosophizing, which 
directs us not to multiply causes when the effects 
appear to be the same. Neither will the laws of 
electricity better solve the phenomena of this ani- 
mated vegetable : for its leaves are equally affected 
by the contact of electric and non-electric bodies ; 
show no change in their sensibility whether the at- 
mosphere be dry or moist ; and instantly close 
when the vapour of volatile alkali or the fumes of 
burning sulphur are applied to them. The powers 
of chemical stimuli to produce contractions in the 
fibi ■es of this plant may perhaps lead some philoso- 
phers to refer them to the vis insita , or irritability, 
which they assign to certain parts of organized 
matter, totally distinct from, and independent of, 
any sentient energy. But the hypothesis is evi- 
dently a solecism, and refutes itself : for the pre- 
sence of irritability can only be proved by the ex- 
perience of irritations; and the idea of irritation in- 
volves in it that of feeling.” 
VOL. III. D 
