150 PHYSIOLOGY OF NUTRITION. 



itself with a precipitation membrane of Cupric ferrocyanide, which 

 becomes stretched since the Copper chloride attracts water from 

 the outside. In this way is formed a turgescent artificial cell 

 (Traube's cell), which, however, rapidly increases in size, and may 

 gradually attain a length of several centimetres. The brown 

 ferrocyanide membrane viz. being stretched, molecules of dis- 

 solved Copper chloride pass into it from the inside, and molecules 

 of Potassium ferrocyanide from the outside. These enter into 

 chemical reaction with one another in the membrane, to form the 

 new molecules of Copper ferrocyanide which really effect the 

 growth of the membrane initiated by its extension. 2 



If we mount on a slide in a drop of water hairs from stamens of 

 Tradescantia, or a piece of leaf epidermis from the plant, or a fila- 

 ment of Spirogyra, and run in glycerine or a solution of sugar from 

 the edge of the cover-glass, the appearances mentioned in 58 are 

 exhibited. The cells pass from the turgescent to the plasmolytic 

 condition. Their protoplasm detaches itself from the cell- wall, 

 and draws itself together, while the cell-sap gives up its water to 

 the water-attracting fluids (glycerine, sugar solution) outside. 

 The cells do not by any means at once die as the result of plas- 

 molysis, as is strikingly shown by the fact that the protoplasm of 

 the plasmolysed cells of the staminal hairs of Tradescantia still 

 remains for a long time impermeable to the violet pigment dis- 

 solved in their cell-sap. 



We must, however, go on to show by experiment that structures 

 made up of many tissues can easily be reduced from a state of tur- 

 gescence to one of plasmolysis. We employ young flower-stalks 

 of Butomus umbellatus and species of Plantago, leaf-stalks of Tro- 

 pifiolum, etiolated epicotyls of Phaseolus, or main roots of this plant 

 (seedlings germinated in sawdust). Pieces are taken 50-100 mm. 

 in length, and on these, at a distance of 40-90 mm., are made fine 

 ink marks. Pieces of root must first be carefully wiped dry with 

 tine linen. We use best Indian ink, rubbed down in water. To 

 make the marks we use a sable hair brush, which must always be 

 kept perfectly clean. After making the marks, we leave the 

 objects for a few minutes in moist air, to make sure that the ink 

 adheres, and then with a millimetre scale measure the intervals 

 between the marks. The objects are then put into a 10 per cent, 

 aqueous solution of common salt or Potassium nitrate. In these 

 solutions they lose their turgidity, pass into a condition of plas- 

 molysis, become limp, and after a longer or shorter time (four to 



