The Physiology of the Ascent of Sap

Co-ordinated action is often met with in the nervous reflex. The four quadrants in the pulvinus of Mimosa act as four different effectors with torsional movements to the right or to the left, and vertical movements up or down. These four quadrants are controlled by separate nervous impulses transmitted from the four sub-petioles bearing the leaflets when stimulated by light. The leaf as a whole is adjusted in space by the co-ordinated action of the four reflexes. The dia-heliotropic attitude of the leaf is thus brought about by distinct nervous impulses, initiated at the perceptive region actuating the different effectors at a distance (p. 254).

There are other modes of stimulation with corresponding nervous reflexes ; and it is the permutation and combin- ation of all these factors, some concordant and others antagonistic, that give rise to the innumerable variations of the resulting responses. This is the secret of the great complexity of the life-movements, which are by no means capricious, but are capable of rational explanation. The ultimate result of investigations such as these is the establishment of the important generalisation of the unity of physiological mechanism in all life. For we find, in the plant and in the animal, similar contractile movement in response to stimulus, similar cell-to-cell propagation of pulsatory movement, similar circulation of fluid by pumping action, similar nervous mechanism for the transmission of excitation, and similar reflex movements at the distant effector. The simpler type of plant-organisation offers an unique advantage in investigation, the pursuit of which will no doubt lead to the solution of many perplexing problems of animal life.

Ascent of sap, independent of root-pressure and transpiration, 36 ; effect of drought on, 36, 45 ; Hght on, 46 ; diminished internal pressure on, 54 ; electric stimulus on, 55 ; tonic condition on, 57 ; variation of temperature on, 58 ; critical temperature for arrest of, 64; effect of anaesthetics on, 69; poison on, 70; determination of, see Velocity; in the stem, 257 Autonomous pulsation, in Desmodiiim, 8 ; continuity with multiple re- sponse, 9 ; in growth, 10 ; characteristics of, 23

Cellular pulsation, discover>^ of, 2H ; in trees, 212 ; period of, 214 ; electro- motive variation of, 213 ; in uni-directioned propulsion of sap, 222 ; effect of stimulus on, 233 ; necessity of stimulus in maintenance of, 234 ; effect of differential hydrostatic pressure on, 236 ; electric current on, 237 ; variation of temperature on, 238 ; anaesthetics on, 239 ; arrest of, under diminished internal pressure, 241 Chloroform, effect of, on pulsation in Desmodium, 19 ; on growth, 20 ; on ascent of sap, 69; on transpiration, 115; on exudation, 140; on cellular pulsation, 239

Chrysanthemum coronarium, effect of drought and irrigation on, 25 ; velocity of ascent in, 45 ; effect of poison on, 69, 70 ; wave-length of pulsation, 237 Contractility of protoplasm, 144 Contraction, 143 Critical minimum temperature, for Desmoditim leaflet and growth, 18 Desmodium pulsation, 8, 209 ; effect of hydrostatic pressure on, 12 ; inhibitory effect of stimulus on, 14 ; tonic condition on, 15 ;. renewal of, by stimulus, 16 ; variation of temperature on, 17 ; critical tem- perature for arrest of, 18, 64 ; effect of anaesthetics on, 18 ; poison on, 21 ; summary, 258

Differential Balance, for discriminating between transpiration and eva- poration, 124 hydrostatic pressure, effect of, on flow of sap, 236 Di-phasic method for determination of velocity of ascent, 203 EiNTHOVEN galvanometer, record of cellular pulsation b3^ 213, 226 Electric maxima and minima, determination of, 223 ; relation to wave- length, 224 Evaporation, role of, 91 ; difference between transpiration and, 129 Excitator}^ impulse, velocity of, 245 ; channel for conduction of. 246

Friction, effect of, on transpiration, 104 ; on activity of root, 234 Geotropism, explanation of positive and negative, 231 Glands of Nepetithes, 95 ; multiple response of, 95 Godlewski, 3 Growth, pulsation in, 10; effect of internal hydrostatic pressuie on, 12 ; stimulus on, 14, 17 ; modifying influence of tonic condition on, 15 ; variation of temperature on, 17, 60 ; critical temperature for arrest of, 18 ; effect of anaesthetics on, 20 ; poison on, 21 ; summary, 25S

Impatieus, effect of drought and irrigation on, 31 ; velocity of ascent of Leaf, determination of transpiring activity of, 86 ; physiological continuity between stem and, 91 ; as catchment-basin for stimulus of light, Light, eft'ect as stimulus, on Desmoditim pulsation, 16. 110; on growth, 17, no; on ascent of sap, 46; on transpiration, 107; on puls-a- tion, 246 effects of blue and red rays on transpiration, in Mimosa piidica, erectile response of, 30 ; expulsion of sap by cells of pul-

vinus, 143 ; hydraulic and nervous reflex in, 247 ; co-ordination of nervous reflexes in, 252 ; distinct effectors in the pulvinus of, 253 ; localisation of nervous connections of subpetioles with pulvinus in, 253 ; dia-heliotropic attitude of, 254 Molecular and cellular model, 191 Molisch, on absence of root-pressure in Palms, 178, 187 Nerve, distribution of, in plants, 245 ; stimulation of internal cortex through transmitted stimulus by, 246 ; in Mimosa, 2.53 Nervous impulse in plants, velocity of, 245

Palms, diurnal variation of exudation, 182, 185 ; action of sunlight on exudation of, 186 ; absence of root-pressure in, 187 ; persistence of exudation after felling of, 188; stimulus for initiation of exudation of, 189, 264 Reflexes, hydraulic and nervous, 244 ; antagonism between hydraulic and nervous, 247 ; co-ordination of, 252 Rhythmic tissues, S ' Ringing ' experiment, 34 Root, continuity of physiological action in shoot and, 141 ; stimulation of,

Stimulus, effect of, on Desmodium pulsation, 14 ; on growth, 14 ; opposite effects of, on normal and sub-tonic tissues, 15; on ascent of sap, 55 ; on cellular pulsation, 259 ,, electric, see Electric stimulus ,, importance of, in maintenance of life-activity, 245 „ effect of, on transpiration from upper and lower surfaces of leaf, 103; on exudation, 138; mechanical, effect of, on root in ascent of sap, 234 for initiation of exudation of Palms, 189, 264 Stomata, action of light on, 108 Strasburger, 3, 22, 75, 77

Sunlight, stimulus of, on ascent of sap, 47, 259 ; on transpiration and internal pressure, 163 ,, thermal effect of, on internal exudation of Mango-tree, 176; on exudation in Palms, 186 Theory of Suction and Root-pressure, 34 Thermal Radiation, effect of, on transpiration, 107 Tilting Electric Recorder for exudation, 133 Timiriazeff, 234 Tonic condition, modifying influence of, in Mimosa, 15 ; on ascent of sap, 57, 259 Transpiration, comparison of, with evaporation, 87, 126; ratio of between upper and lower leaf-surfaces, 87 ; from a single stoma, 88 ; inde- pendent of evaporation, 89 ; effect of variation of temperature on, Q2 ; electric stimulation of lamina, petiole and midrib on, 93, 102 ; diminished turgor on, 102 ; mechanical stimulation on, 103 ; Tesla current on, 105 ; electric induction on, 106 ; electric waves on, 106 ; thermal radiation on, 107 ; light on, 107, no; red and blue-violet light on, III ; carbonic acid on, 113; ether vapour on, 114 ; chloroform on, 115 ; diurnal variation of, 118 ; effect of removal of root on, 119; optimum temperature for, 128 ; summary, 265

Velocity of ascent of sap, eflect of various conditions in modification of, 40 ; influence of previous history of plant on, 41 ; effect of drought on, 45 ; effect of stimulus of sunhght on, 46 ; deter- mination of, in normal, reverse and trans- verse directions, 48 ; effect of diminished internal pressure on, 54 ; electric stimulus on, 55 ; tonic condition on, 57 ; variation of temperature on, 58 ; anaesthetics on, 69 ; removal of root on, 79 ; summary, 263 ,, ,, ,, determination of, by mechanical method, 25;

Wave-length, determination of hydrauhc, 222 ; change 01, under XvLEM, effect of injection of air into, 37 ; function of, as reservoir, 38, 262 ; physical convection of sap in, 38 ; lateral pumping of sap into, 38, 175 ; absence of active cells in, 219