CH, V] TURGOR. 113 



by the formation of a precipitation membrane the osmotic 

 quality of the parchment is changed. 



(145) Absorption of methylene blue. 



It is interesting to note in connection with the last 

 experiment that methylene blue, as Pfeffer' has shown, 

 can pass a living protoplasmic membrane. 



Two or three sprigs of El odea are placed in about a 

 liter of tap- water containing 0*0008 per cent, of methylene 

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

 found to contain blue cell ssTp. 



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 °/o NaCl 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 



^ Untersuchungen aus dem Bot. Institut zu Tubingen, ii. p. 223. 

 D. A. 8 



