CONTENTS
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]
PART II.
GROWTH AND ITS RESPONSIVE VARIATIONS.
X.—THE HIGH MAGNIFICATION CRESCOGRAPH FOR RESEARCHES ON GROWTH.
Method of high magnification—Automatic record of the rate of growth—Determination of the absolute rate of growth—Stationary method of record—Moving plate method—Precaution against physical disturbance—Determination of latent period and time-relations of response—Advantages of the Crescograph—Magnetic amplification—The Demonstration Crescograph[151]
XI.—EFFECT OF TEMPERATURE ON GROWTH.
Method of discontinuous observation—Method of continuous observation—Determination of the cardinal points of growth—The Thermocrescent curve—Relation between temperature and growth[173]
XXII.—EFFECT OF CHEMICAL AGENTS ON GROWTH.
Effect of stimulants—Effect of anæsthetics—Action of different gases—Action of poisons[183]
XIII.—EFFECT OF VARIATION OF TURGOR AND OF TENSION ON GROWTH.
Response to positive variation of turgor—Method of irrigation—Effect of artificial increase of internal hydrostatic pressure—Response to negative variation of turgor—Method of plasmolysis—Effect of alternative variations of turgor on growth—Response of motile and growing organs to variation of turgor—Effect of external tension[188]
XIV.—EFFECT OF ELECTRICAL STIMULUS ON GROWTH.
Effect of intensity—Effect of continuous stimulation—Continuity between ‘incipient’ and actual contraction—Immediate effect and after-effect[195]
XV.—EFFECT OF MECHANICAL STIMULUS ON GROWTH.
Effect of mechanical irritation—Effect of wound[200]
XVI.—ACTION OF LIGHT ON GROWING ORGANS.
Method of experiment—Normal effect of light—Determination of the latent period—Effect of intensity of light—Effect of continuous light—Effects of different rays of the spectrum[205]
XVII.—EFFECT OF INDIRECT STIMULUS ON GROWTH.
Mechanical and electrical response to Indirect Stimulus—Variation of growth under Indirect Stimulus—Effects of Direct and Indirect Stimulus[213]
XVIII.—RESPONSE OF GROWING ORGANS IN STATE OF SUB-TONICITY.
Theory of assimilation and dissimilation—Unmasking of positive effect—Modification of response under artificial depression of tonic condition—Positive response in sub-tonic specimen—Abnormal acceleration of growth under stimulus—Continuity between abnormal and normal responses—Positive response to sub-minimal stimulus[219]
XIX.—RESUMPTION OF AUTONOMOUS PULSATION AND OF GROWTH UNDER STIMULUS.
Resumption of pulsatory activity of Desmodium leaflet at standstill—Renewal of growth under stimulus—General laws of effects of Direct and Indirect Stimulus[227]
XX.—ACTION OF LIGHT AND WARMTH ON AUTONOMOUS ACTIVITY.
The Oscillating Recorder—Record of pulsation of Desmodium gyrans—Effect of diffuse light in diminution of amplitude and reduction of diastolic limit of pulsation—Antagonistic action of warmth in reduction of systolic limit[233]
XXI.—A COMPARISON OF RESPONSES IN GROWING AND NON-GROWING ORGANS.
Contractile response of growing and non-growing organs—Time-relations of mechanical response of pulvinated and growing organs—Similar modification of response under condition of sub-tonicity—Opposite effects of Direct and Indirect stimulus—Exhibition of negative electric response under Direct, and positive electric response under Indirect stimulus—Similar modification of autonomous activity in Desmodium gyrans and in growing organs under parallel conditions—Similar excitatory effects of various stimuli on pulvinated and growing organs—Similar discriminative excitatory effects of various rays in excitation of motile and growing organs—Action of white light—Action of red and yellow lights—Action of blue light—Action of ultra-violet rays—Action of infra-red rays—Diverse modes of response to stimulus—Mechanical response—Electromotive response—Response by variation of electric resistance[239]