

292 BOTANICAL GAZETTE (april 



Table V shows that the second crop Bartlett pears designated 

 as lot 5 were of especial interest, in that they remained unripe 

 for a relatively longer period than any of the other lots. Lot 5 

 was in the Freas oven at a temperature of 101 F. and surrounded 

 by a relative humidity below 50 per cent until November 5. On 

 this date, nearly 6 weeks after the beginning of the experiment, 

 the pears were still unripe. When compared with fruits stored 

 at room temperatures, this shows a delay in ripening of a little 

 over 4 weeks. This lot also is of interest in that it indicates that 

 it is a question of high temperature only, which causes the ripen- 

 ing processes to be inhibited, and that high relative humidity has 

 no marked influence, except to lessen the amount of wilting. 



The question arises why the fruit of lot 5 should keep longer than 

 the fruit of lots 2 and 3, since the temperatures in each case were 

 all comparatively high. The chief difference between these lots 

 was the much lower relative humidity of lot 5 , as contrasted with * 

 lots 2 and 3. It is probable that the greater desiccation or wilting 

 of the pears of lot 5 did retard their ripening, but two other points 

 should be mentioned. (1) When the relative humidity was high, 

 much trouble was experienced from molds infecting the fruit and 

 causing it to rot. There was no loss from rot in lot' 5, due no 

 doubt to the very low humidity. (2) The temperature of lot 3 

 was no doubt too high, and it is probable that the temperature 

 surrounding lot 2 was somewhat below the optimum temperature 

 for the retardation of the ripening. 



Specimens from lot 5 were tested by Dr. J. Rudisch and the 

 senior author to determine if any enzymes were active. The 

 tissue was treated with a tincture of guiac and gave no test for 

 oxidase, either with or without the addition of hydrogen peroxide; 

 neither could a test for an organic peroxide be shown upon the 

 addition of a solution of potassium iodide, weak acid, and starch 

 solution, as indicated by the liberation of free iodine and the 

 consequent blueing of the starch solution. This might indicate 

 that the higher temperatures had destroyed or inhibited the action 

 of the ferments or enzymes normally present in the tissue of pears. 

 This resulted in a checking of the ripening process with a con- 

 sequent prolonging of the period in which the fruit could be kept. 



