212 W. A. CANNON 



plasmolysis of these cells did not occur. The epidermal cells of 

 the young roots did not plasmolyze in 0.5 N KNO3 solution, but 

 a stronger solution, 0.75 N, brought this about. 



On the following day the tests were repeated. At this time 

 only occasional epidermal cells of the leaves were plasmolyzed 

 with a normal solution of the salt, but plasmolysis of all of the epi- 

 dermal cells was effected in a 1.5 N KNO3 solution. The temper- 

 ature of the solutions used on the two days was the same. The 

 epidermal cells of the roots, on the other hand, were plasmolyzed 

 in a 0.5 N solution. No explanation is attempted of the diver- 

 gency of results with Peganum. 



All of the material available was examined and, so far as pos- 

 sible, under parallel conditions. The results show that in the same 

 individual cell sap of the roots is less dense, in the last instance 

 much less dense, than it is in the shoots. The general result shows 

 a somewhat less dense cell sap than Fitting found for the same 

 species at Biskra. For example, specimens of Peganwn from the 

 Sahara showed the following reactions : An occasional epidermal 

 cell on the upper side of the leaves was plasmolyzed in a 1.2 GM 

 KNO3 solution, while all of the cells of the epidermis of the upper 

 portion of the leaf, anda few of the palisade cells of the leaf, were 

 plasmolyzed in a 2 GM KNO3 solution. Specimens from culti- 

 vated lands, at the moment not tilled, were affected by solutions 

 varying from 0.7 to 0.9 GM KNO3. Specimens from the dunes, 

 on the other hand, had a somewhat heavier cell sap, as it required 

 solutions varying from 1 to 1.2 GM KNO3 to effect plasmolysis 

 of the epidermal leaf cells. 



