Bitter Pit in Apples. 383 



One per 10,000. From none to several mainly superficial pits, 

 none exceeding \ mm. deep and 1 mm. diameter. 



One per 100,000. No perceptible effect. 



At this stage apples have the cuticle very feebly developed, 

 the bloom absent, and the minute temporary breathing pores 

 (stomata) have not yet been replaced by the larger adult ones 

 (lenticels). The skin is therefore more or less generally perme- 

 able to poison, and the pits are developed without any relaition 

 to breathing pores. The permeability of the skin is also shown 

 by the fact that in fairly dry air the apples after picking 

 undergo a pronounced loss of weight in one day, and in tliree 

 to seven days begin to shrivel. 



With prepared apples the young pulp cells showed themselves 

 to be very much more resistant than the pulp cells of adult 

 apples. 



One per 10,000. Strongly marked but mainly superficial pits 

 beneath each prepared spot, none exceeding 2 mm. diameter and 

 1 mm. depth. 



One per 100,000. Superficial layers browned and killed at 

 each prepared spot, but no distinct pit formation. 



One per 1,000,000, From no perceptible effect to distinct but 

 entirely superficial browning (two to three layers of cells urown 

 and dead). 



One per 10,000,000. No perceptible effect. 



In dry air the prepared areas show a tendency to cork for- 

 mation, but not in water or in moist air. These results show 

 that while in these young apples the skin is more readily per- 

 meable than in adult ones, the pulp cells are some hundred 

 times more resistant to such a poison as lead nitrate. Hence 

 sufficient poison might enter a young apple to produce internal 

 poisoning when adult, without showing any signs of its pre- 

 sence at first, beyond hindering or preventing the solution of 

 deposited starch grains. Later on the affected cells would die, 

 not so much because the poison increased in amount as because 

 the resistance of the cells decreased with age. It is worthy 

 of note in this connection that these young Jonathan apples three 

 or so weeks old contain plenty of active chloroplastids par- 

 ticularly in the outer layers, but no starch grains either in the 

 healthy pulp or superficial cells, or in the poisoned pit cells. 



