242 Alfred J. Eivart: Bitter Fit. 



sap from solution, and in cells bruised while in the starch stage, 

 will aid in preventing the starch from dissolving. In the bitter 

 pit cells, however, the starch grains are in the protoplasm, and 

 so long as the latter is living the tannic acid of the cell-sap is not 

 in contact with them, or with diastase. If any of the tannic is 

 present in the protoplasm, it exists in the form of special small 

 vacuoles, and is also not in contact with the starch or diastase. 

 It is probably the difficulty of penetration which makes externally 

 applied tannic acid non-poisonous in dilutions below 1 per 1000. 

 Diastase solution after prolonged contact with pounded apple pulp 

 loses its solvent action. 



In the presence of tannic acid a small quantity of starch is 

 easily overlooked by the iodine test, apart from its precipitation. 

 It was possibly in this way that Rothera and Greenwood obtained 

 an apparent acceleration of diastatic action after contact with 

 apple pulp. Their results are therefore of no value so far as the 

 poisoning theory of bitter pit is concerned. A complete exhaus- 

 tive numerical analysis of the mineral constituents of bitter pit 

 tissue in bulk is urgently needed, paying special attention to 

 metallic elements present in small amount, and this would prob- 

 ably give definite guidance for further investigation. The nature 

 of the combinations in whicli the mineral constituents occur will 

 also be of importance. Thus approximately 1 per cent, of the 

 ash may consist of oxide of iron- If this were present, either as 

 the chlorides or sulphates, it would be distinctly poisonous. 



EXPLANATION OF PLATES XXIII. 



Potatoes halved after four days in 5 per cent, lead nitrate. 



a and d, face view, b and c. side view of cut lialf. 



Two fragments of skin were removed on c and d, and three larger 

 ones on a and b prior to immersal. 



The poison was absorbed from the surface, but the browning is 

 deep-seated. 



