538 EDMUND NEWTON HARVEY 



Ammonia: Red stained Elodea leaves are placed in ^ NH4OH. 

 Cells becon\e yellow in less than one minute. Rotation ceases at the 

 time the color change begins (f min.). After 1 min. the alkali is re- 

 placed by water. The bright red color begins to return (20-25 mins.) 

 and the cells are as red as they were originally in 1 hour. In 1 hour, 

 10 mins. jerky rotation begins and in 2 hours the original rapid ro- 

 tation may be observed. 



Sodium hydrate: Red stained Elodea leaves are placed in ^ NaOH 

 under the microscope. Rotation ceases in about one minute, begins 

 again slowly in 5-10 minutes, stops again after 15 minutes longer, and 

 the red sap only begins to turn dull pink to yellow after 45 minutes to 

 1 hour. If the alkali is replaced by water, the sap never becomes red 

 again and rotation never returns. 



e. The effect of added substances on the penetration of NaOH 

 and KOH. As indicated in table 4 even chloroform treatment 

 hardly increases the rate with which NH4OH may enter Elodea 

 cells. Ammonia enters living cells as rapidly as dead ones. 

 NaOH enters dead cells nearly as rapidly as ammonia, but living 

 cells offer a high resistance to its passage. This resistance may be 

 decreased by the addition of chloroform to the medium in amounts 

 too small to have any irreversible effects in the absence of NaOH. 

 On comparing the time for NaOH or KOH to decolorize red 

 stained Elodea leaves in ^o solution alone and in to solution plus 

 dilute chloroform, alcohol, urea, glycerine, and various salts it 

 is found that all have the effect of shortening the time which it 

 takes for the NaOH to enter. The analysis of the experiment is 

 somewhat complex. The effect of the added substance may be 

 on the plasma membrane or on the alkali (affecting its dissocia- 

 tion or combining to form more toxic compounds) ; or the alkali 

 may allow the more read>' entrance of the added substance with 

 consequent rapip destructive action and death of the cell which 

 leads also to easy penetration of alkali. In other words, the action 

 of two substances together may be additive. 



On account of the complexity and difficulty of interpreting 

 results I discontinued further experimentation along this line. 

 A few experiments are given. The effect of dilute chloroform 

 solution must be attributed to decrease in resistance of the cell 



