SENSITIVE PLANT. 
299 
The plant was then carried into the open air, where, 
after remaining a night, it was perfectly recovered, 
without having been at all weakened by its late 
usage, or having lost any of its former sensibility.” 
By this experiment, which is not the only one 
that was made, it is pretty clear that neither light 
nor darkness has any sensible effect upon the sen- 
sitive plant ; it is not so passive, however, under the 
different degrees of temperature. In a place which 
has been greatly heated, and where the thermometer 
will suddenly rise several degrees, the mimosa will 
shut sooner than when in the open air: — “ from hav- 
ing observed this to take place several times, we are 
led to suppose that the cause of its spontaneous mo- 
tion is the great and sudden changes of temperature 
which so commonly take place in our climate : this 
opinion may be easily put to the proof ; for if a 
plant of this species be raised under a bell-glass, ex- 
posed to the heat of the sun, it will close almost the 
moment it is uncovered, provided the external air is 
in a much cooler state.” 
Nevertheless, though heat and cold contribute 
greatly towards its alternate motion, yet the plant is 
certainly less sensible, or more sluggish in its move- 
ments, during the winter. In a good green house, 
indeed, it will continue to contract through the 
whole of this inclement season ; but then its func- 
tions seem to be considerably impaired, and it moves 
with less vivacity. 
After a branch has been separated from the shrub 
the leaves still retain their sensibility, and will shut 
