180 EXCHANGES AND MOVEMENTS OF FLUIDS 



249. Plasmolysis. Mount a filament of Spirogyra, hair from 

 Cucurbita, Tradescantia, Lycopersicum, or a portion of the epidermis 

 of a young plant in distilled water. Note the condition of the 

 total inclusion of the cell, and movement if present. Place a drop 

 of 5 per-cent. solution of potassium nitrate at one side of the 

 cover-glass, and draw out the water from the other side with a 

 strip of blotting paper. Note effect on cell. Draw and replace 

 the preparation in distilled water as before, noting result. 



250. Permeability of Plasmatic Membranes to Coloring Matter. 

 Fill a large culture dish with a solution of water and methyl-blue, 

 in the proportion of one to a hundred thousand, and in it place 

 filaments of Spirogyra, and sprigs of Philotria, allowing them to 

 remain 24 to 48 hours. Examine with magnification of 400 to 

 500 and note the presence of coloring matter in the vacuoles, 

 showing that the methyl-blue has passed the membranes of the 

 cytoplasm without the latter being stained. The accumulation 

 of the dye in the vacuoles is due to the fact that it is converted 

 here into a form to which the plasma is not permeable. It forms 

 precipitates in Spirogyra, but remains fluid in Philotria} 



251. Osmose ; Change in Osmotic Qualities of Membrane Af- 

 fecting Permeability. Soak a section of parchment tubing 2 5 cm. 

 long and 5 cm. in diameter, in water for an hour, than pleat a 

 small section at one end, double back and tie firmly with a wrap- 

 ping of cord. If parchment capsules are procurable this will be 

 unnecessary. Fit a perforated cork or rubber stopper to the other 

 end and secure it firmly with many wrappings of cord. Next 

 provide a separatory funnel fused to the horizontal arm of a T 

 tube. Insert one free arm of the T tube in the perforation in the 

 stopper and to the other end fit a capillary tube by means of a 

 section of rubber tubing bound with wire. The capillary tube 

 may be 2 m. in length and should be held upright by suitable 

 supports. Fill the parchment tube with a saturated solution of 

 cane sugar, then close the stopcock of the funnel. Immerse the 



1 For full discussion of the entire subject see Pfeffer's Plant Physiology, 1 : 70- 

 174. 1900. Also see appendix. 



