Chapter II: Part I: Response of Plant Organs

I.--THE PROBLEM OF MOVEMENT IN PLANTS.

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Complexity of the problem--Effects of different forms
of stimuli--Diverse responses under identical
stimulus--Modification of response determined by intensity
and point of application of stimulus, and tonic condition of
organ--Response of pulvinated and growing organs--Necessity
for shortening the period of experiment 1

II.--THE “PRAYING” PALM TREE.

Description of phenomenon--The Recording apparatus--Record
of diurnal movement of the tree--Universality of tree
movement--Cause of periodic movement--Periodic movement
of trees, and diurnal variation of moto-excitability
in _Mimosa pudica_--Relative effects of light
and temperature--Physiological character of the
movement--Transpiration and diurnal movement--Diurnal
movement in inverted position--Effect of variation of
temperature on geotropic curvature--Reversal of natural
rhythm by artificial variation of temperature 5

III.--ACTION OF STIMULUS ON VEGETABLE TISSUES.

Different types of Response Recorders--Response of a radial
organ--Response of an anisotropic organ--Response of pulvinus
of _Mimosa pudica_--Tabular statement of apex time and
period of recovery in different plants--Response of pulvinus
of _Mimosa_ to variation of turgor--Different modes of
stimulation 31

IV.--THE DIURNAL VARIATION OF EXCITABILITY IN _MIMOSA_.

Apparatus for study of variation of excitability--Uniform
periodic stimulation--The Response Recorder--Effects of
external condition on excitability--Effects of light
and darkness--Effect of excessive turgor--Influence of
temperature--Diurnal variation of excitability--Effect of
physiological inertia 43

V.--RESPONSE OF PETIOLE-PULVINUS PREPARATION OF _MIMOSA_.

Effect of wound or section in modification of normal
excitability--The change of excitability after immersion in
water--Quantitative determination of the rate of decay of
excitability in an isolated preparation--Effect of amputation
of upper half of the pulvinus--Effect of removal of the lower
half--Influence of weight of leaf on rapidity of responsive
fall--The action of chemical agents--Effect of “fatigue” on
response--The action of light and darkness on excitability 73

VI.--CONDUCTION OF EXCITATION IN PLANTS.

Hydro-dynamic _versus_ physiological theory of conduction
of excitation--Arrest of conductivity by physiological
blocks--Convection and conduction of excitation--Effect
of temperature on velocity--Effect of season--Effect of
age--Effect of dessication of conducting tissue--Influence
of tonic condition on conduction--Effect of intensity
of stimulus on velocity of transmission--Effect
of stimulus on sub-tonic tissues and tissues in
optimum condition--Canalisation of conducting path by
stimulus--Effect of injury on conductivity 97

VII.--ELECTRIC CONTROL OF EXCITATORY IMPULSE.

Method of conductivity-balance--Control of transmitted
excitation in _Averrhoa bilimbi_ by electric
current--‘Uphill’ transmission--Transmission
‘downhill’--Electric control of nervous impulse in
animal--Directive action of current on conduction of
excitation--Effects of direction of current on velocity
of transmission in _Mimosa_--Determination of variation
of conductivity by method of Minimal Stimulus and
Response--Influence of direction of current on conduction
of excitation in animal nerve--Variation of velocity of
transmission--After-effects on Heterodromous and Homodromous
currents--Laws of variation of nervous conduction under
electric current 107

VIII.--EFFECT OF INDIRECT STIMULUS ON PULVINATED ORGANS.

Conduction of excitation--Dual character of the transmitted
impulse--Effect of distance of application of
stimulus--Periods of transmission of positive and negative
impulses--Effects of Direct and Indirect stimulus 135

IX.--MODIFYING INFLUENCE OF TONIC CONDITION ON RESPONSE.

Theory of assimilation and dissimilation--Unmasking of positive
effect--Modification of response under artificial depression
of tonic condition--Positive response in sub-tonic specimen 141