16 



THE CAUSES OF FLUCTUATIONS IN TUEGESCENCE 



to the action of anaestlu 

 produce the same effect. 



and the next one shows that 



>ly low tempo ratur 



Experiment 



china* 28*75 grammes, was put into a 



XL — A large leaf of Kalanchoe, wei - — 



and salt. On being removed 



metal box and buried in a mixture of pounded ice 



afte 



r 



an interval of an hour and a quarter it was found to be rigidly frozen, but without 



visible exudation or change of colour. 



It was now set in a hermetically closed chamber, 

 On the following day it had acquired a yellowish 



and very soon began to sweat visibly. 



tint and was quite flaccid and moist. The weight was now only 24*16 grammes 



i 



corre- 



sponding to a 



grammes 



* 



giving 



loss of 4*59<?.<?. of fluid, and on the following day was only 22*55 

 a total loss of 21*5 per cent, on the original weight. The only 



difference presented by the phenomena in this case as compared with those occurring in 



cases 



of aneesthesia was the primary absence of exudation ; but this is readily accounted 



for if it be taken into account that any 

 initial stages of the 



liquid entering 



the intercellular spaces in the 

 experiment must have been frozen as it approached the surface of 



the leaf, and so have plugged the stomatic orifices. 



It is not, however, merely anaesthetics and excessive elevation or depression of 

 temperature which produce such results, for essentially similar ones occur in cases where 

 the tissues are exposed to strong acid or alkaline vapours, to immersion in solutions of 

 corrosive sublimate, or to the influence of electrical currents or discharges. 



I have not personally tried any experiments on the action of electrical currents on 

 vegetable tissues, but the accounts which are furnished by Becquerel* regarding the 

 results of his investigations of the subject leave no doubt that they also give rise to a 

 loss of turgescence. He found that, in the case of milky Euphorbias, treatment of the 

 shoots with electrical discharges was followed by a suppression of the discharge of latex 



phenomenon which can only have been due to loss of turges- 



mcision, a 



on subsequent 



cence in the milk tubes. When leaves of Begonia discolor, which are red on one face 

 and green on the other, were subjected to electrical currents, the red face became 

 sensibly green and the green one red, due to escape of the red fluid from the interior 



diffusion throughout the intercellular 



spaces 



finding that there was no 



of the cells normally containing it and its 



of the tissue. He was at first inclined to explain the escape of liquid from the cells 

 as due to rupture of the walls of the latter under the influence of the electricity; but, 



microscopical evidence of rupture, he ultimately came to 

 the conclusion that the phenomenon was due to alterations in the nature of the 

 cell-sap. 



The following experiments illustrate the effects produced by exposure of the tissues 

 to poisonous vapours and solutions: 



Experiment XIL—A leaf of Kalanchoe, weighing 10-03 grammes, was set in a carbonic 

 acid chamber. The first result which manifested itself was a certain amount of inten- 

 sification of the green colour of the tissue, but the surface gradually became moist, and 

 within a quarter of an hour actual exudation of drops of liquid had occurred. On the 



following day the leaf 



was of a dull, ochreous brown colour 



grammes. 



It was returned to the chamber, and twenty-four hours later 



and weighed only 8*9 



was 



almost 



* " Des Forces Physieo-Chimiques." Paris, 1876. 



