According to varying circumstances, the same blow will evoke responses
of different amplitudes. Early in the morning, after the prolonged
inactivity of a cold night, we find the plant inclined to be lethargic,
and its first answers correspondingly small. But as blow after blow is
delivered, this lethargy passes off, and the replies become stronger and
stronger. A good way to remove this lethargy quickly, is to give the
plant a warm bath. In the heat of the midday, this state of things is
reversed. That is to say, after giving vigorous replies the plant
becomes fatigued, and its responses grow smaller. This fatigue passes
off, however, on allowing it a period of rest. On increasing the
intensity of the impinging stimulus, the response also increases. But a
limit is attained, beyond which response can no longer be enhanced.
Again, just as the pain of a blow persists longer with ourselves, in
winter than in summer, so the same holds good of the reaction of the
plant also. For instance, in summer it takes _Mimosa_ ten to fifteen
minutes to recover from a blow, whereas in winter the same thing would
take over half an hour. In all this, you will recognise the similarity
between human response and that of the plant.