418 Martin: Effect of concentrated solutions 



(3) 9^V-*^ potassium nitrate'was required to produce plasmoly- 

 sis in leaves which had been in «/3 urea about seven hours. 



Acetaniid. — Since recovery from plasmolysis by acetamid usu- 

 ally occurs in a few minutes, the tests for increase in concentra- 

 tion of the sap were made upon the same cells soon after turgidity 



was restored. 



(i) w/3 acetamid showed incipient plasmolysis. The cells 



were slowly replasmolyzed by 7^/3 potassium nitrate, in- 



cipiently at the apex, but stronger toward the base. 



(3) ni2 acetamid plasmolyzed nearly all cells. It required 



from ;?/3 to ///2 potassium nitrate to replasmolyze such cells. 



Tradcscantia discolor 



Free-hand sections were cut from the lower epidermis of Trad- 

 escantia discolor^ whose cells have a red or violet-colored sap. 

 These were mounted directly in the plasmolyzing solutions. The 

 experiments showed a remarkable variation in the reaction of indi- 

 vidual cells of a section, even in the same solution. In some 

 merely incipient plasmolysis was produced, in others the action 

 was quite strong. The cells over a vein were often more easily 

 plasmolyzed than those between the veins. 



Potassium nitrate. Isotonic concentration, — From nj^ to ;//6 po- 

 tassium nitrate was required to produce plasmolysis in Tradcscantia, 

 The action was more uniform with the nj^ solution. 



Glycerine, {a) Isotonic concentration. — From nj^ to njs gly- 



to produce plasmolysis. nj^ glycerine plas- 

 molyzed most of the cells incipiently, whereas nj^. glycerine 

 plasmolyzed all the cells clearly, some completely. 



{b) Increase in concentration of cell-sap. 



(i) In sections which had been in ;//5 glycerine from six to 



necessary 



'/5 



in most cells, though slight plasmolysis appeared in a few 



cells. 



( 



Urea, (a) Isotonic concentration. — w/5 to ??/6 urea produced 

 plasmolysis. The degree varied considerably with both solutions. 



[b) Increase in concentration of cell-sap. — Sections of the lower 

 epidermis of Tradcscantia leaves were pijt in w/5 and in /^/6 urea, 

 and left seven or eight hours. 



