Electric response to direct and indirect stimulation-- Experimental arrangement for obtaining geo-electric response--Geo-electric response of the upper and lower sides of the organ--Method of Axial Rotation--Characteristics of geo-electric response--Physiological character of geo-electric response--Effect of differential excitability of the organ--Law determining the relation between angle of inclination and geotropic effect--Method of Vertical Rotation--Electric response through an entire cycle-- Relation between angle of vertical rotation and intensity of geo-tropic reaction 442 XLI.--MECHANICAL AND ELECTRICAL RESPONSE OF ROOT TO VARIOUS STIMULI. Mechanical and electrical response to Direct stimulation-- Mechanical and electrical response to Indirect stimulation-- Effect of unilateral stimulation applied at the root-tip 461 XLII.--GEO-ELECTRIC RESPONSE OF ROOT. Geo-electric response of the root-tip--Electric response in the growing region of root--Differential effect between the tip and the growing region--Geo-perception at the root-tip 467 XLIII.--LOCALISATION OF GEO-PERCEPTIVE LAYER BY MEANS OF THE ELECTRIC PROBE. Principle of the method of electric exploration--The Electric Probe--Electric exploration of the geo-perceptive layer--Geo-electric reaction at different depths of tissues--Microscopical examination of the maximally excited layer--Influence of season on geo-electric response--Tests of insensitive specimens--Reaction at lower side of the organ--The Method of Transverse Perforation 478 XLIV.--ON GEOTROPIC TORSION. Arrangement for torsional response--Algebraical summation of geotropic, and phototropic effects--Balance of geotropic by phototropic action--Comparative balancing effects of white and red lights--Effect of coal gas on photo-geotropic balance 503 XLV.--ON THERMO-GEOTROPISM. Necessary conditions for geotropic curvature--Modifying influence of temperature on geotropic curvature--Magnetic analogue--Tropic equilibrium under varying intensities of stimulus--Effect of variation of temperature on geotropic torsion--Variation of apo-geotropic curvature under thermal change--Effect of variation of temperature on dia-geotropic equilibrium 509 PART IV. NIGHT AND DAY MOVEMENTS IN PLANTS. XLVI.--DIURNAL MOVEMENTS IN PLANTS. Complexity of the problem--The different factors involved-- Autonomous movements--Epinasty and hyponasty--Positive and negative thermonasty--Thermo-geotropism--Classification of diurnal movements--Discriminating tests for classification-- Diurnal variation of light and of temperature 523 XLVII.--DIURNAL MOVEMENT DUE TO ALTERNATION OF LIGHT AND DARKNESS.