CH. V] TURGOR. 125 



blue, after from 24 to 36 hours the living cells will be 

 found to contain blue cell sap. 



SECTION B. Turgor. 



(146) Plasmolysis, microscopic observation*. 



In order to realise the existence of turgor the well- 

 known microscopic observation of the effect of salt 

 solution on turgescent tissues should be repeated. Plas- 

 molysis is easily seen in Spirogyra, or any tissue with 

 coloured cell sap may be used ; it is only necessary to 

 irrigate a preparation with 5 % XaCl solution. It is 

 instructive to compare the result of plasmolysis with the 

 change produced by death. In the first case the cell sap 

 remains within the protoplasmic sac, in the killed cell it 

 escapes and moreover stains the dead protoplasm. 



(147) Recovery after plasmolysis. 



It is important to realise that plasmolysed parts are in 

 no way injured, and that they recover their normal 

 condition when the plasm olysing fluid is replaced by 

 water. A few simple observations on roots of V. faba 

 serve for this purpose. A bean root 2 3cm. in length 

 is placed in 5 /o NaCl solution, where it almost im- 

 mediately becomes soft and flaccid. When replaced in 

 water it quickly becomes turgid again 2 . 



1 De Vries, Untersuchungen ilber Zellstreekung, 1877. 



2 We have observed that the root of the bean, if placed alternately in 

 salt solution and water several times, becomes translucent, being in fact 

 injected with water. 



