382 Alfred J. Eivart : 



One per 100,000 (250 c.c. of solution)^. Well developed, but 

 small pits, none exceeding 3-4 mm. diameter and 1-2 mm. 

 depth. Numerous minute black spots on skin, but the p\ilp 

 quite sound. 



One per 500,000. As above, but no spots on the skin. 



One per 2,500,000. Pits barely exceeding 1 mm. depth, and 

 not spreading laterally beyond the prepared spots. 



One per 25,000,000. From superficial browning to a few pits 

 1 mm. deep. 



One per 100,0'00,000. Superficial browning on most, but not 

 all, of the prepared spots. 



One per 1,000,000,000. No signs of any poisoning action on 

 any of the prepared spots. 



One point specially noticeable is, that with very dilute solu- 

 tions, the quantity of solution is as important as its concentra- 

 tion. Thus a litre of 1 per 500,000 exercises the same action as 

 250 c.c. of 1 per 100,000, and a litre of 1 per 200,000, which 

 contains twice as much poison as 250 c.c. of 1 per 100,000 also 

 exercises a greater poisonous action when the same area of 

 apple pulp is exposed to it for a sufficient length of time. 



All varieties are not equally sensitive. Thus prepared Rome 

 Beauties kept in the solution one week, and examined after 

 two weeks, showed only superficial broAvning to pits under 1 milli- 

 metre deep in a solution of 1 per million, and no perceptible 

 effect in a solution of 1 in 10 millions. 



The influence of age. 



In order to determine the influence of age upon the sensitivity 

 to poison, young Jonathans about three weeks old were selected, 

 averaging 3 cm. in length by 2 cm. in diameter. They were 

 immersed in solutions of lead nitrate for one week, and after 

 being kept in moist air for a week were examined. 



Apples with the normal uninjured surface gave the following 

 results with lead nitrate : — 



One per 1000. Numerous small ])its with irregular edges, 

 mainly superficial, and none exceeding 1 mm. deep and 2 mm. 

 diameter. 



1 In all cases where not otherwise stated, 1 litre of the solution was used to each apple, 

 which approximates to the amount of water an apple of 100 c.c. bulk may absorb from the 

 tree durinjf its development. 



