ears
of effort, become actual fact. It is unnecessary to tell here of many a
fruitless and despairing attempt. Nor shall I trouble you with any
account of intricate mechanism. I need only say that with the aid of
different types of apparatus, it is now possible for all the responsive
activities of the plant to be written down. For instance, we can make an
instantaneous record of the growth and its variations, moment by moment.
Scripts can be obtained of its spontaneous movement. And a recording arm
will demarcate the line of life from that of death. The extreme delicacy
of one of these instruments will be understood, when it is said that it
measures and records a time-interval so short as one-thousandth part of
a second!

It has been supposed that instruments for research of this delicacy and
precision, were only possible of construction in the best scientific
manufactories of Europe. It will therefore be regarded as interesting
and encouraging to know that every one of these has been executed
entirely in India, by Indian workmen and mechanicians.

With perfect instruments at our disposal, we may proceed to describe a
few amongst the many phenomena which now stand revealed. But before
this, it is necessary to deal briefly with the superstition that has led
to the division of plants into sensitive and insensitive. By the
electrical mode of investigation, it can be shown that not only Mimosa
and the like, but all plants of all kinds are sensitive, and give
definite replies to impinging stimuli. Ordinary plants, it is true, are
unable to give any conspicuous mechanical indication of excitement. But
this is not because of any insensitiveness, but because of equal and
antagonistic reactions which neutralise each other. It is possible,
however, by employing appropriate means, to show that even ordinary
plants give mechanical replies to stimulus.

THE DETERMINATION OF THE LATENT PERIOD

When an animal is struck by a blow, it does not respond at once. A
certain short interval elapses between the incidence of the blow, and
the beginning of the reply. This lost time is known as the latent
period. In the leg of a frog, the latent period according to Helmwoltz,
is about one-hundredth of a second. This latent period, however,
undergoes appropriate variation with changing external conditions. With
feeble stimulus, it has a definite value, which, with an excessive blow,
is much shortened. In the cold season, it is relatively lon