274 BOTANICAL GAZETTE [april 



employment of cold storage and the utilization of low temperatures 

 for the purpose of delaying the ripening of fruit . On the other 

 hand, they seem to be in accord with certain observations which 

 indicate that high temperatures, as well as low, may tend to retard 

 the ripening process of fruit. In this connection the following 

 observations of the writers are of interest. 



When certain varieties of plums and cherries, early in their 

 development upon the trees, are inclosed in closely woven, black 

 sateen cloth sacks, there is a delay of 4 or 5 days in the attainment 

 of maturity, and a prolonging of the period of edibility from 5 to 

 8 w r eeks after the crop of exposed fruits is normally harvested and 

 eaten (7). At the time these data were presented, it was believed 

 that light exclusion was the responsible factor; but in view of 

 Shamel's observations, it might have been high temperatures and 

 high relative humidity in the area surrounding the fruits as a 

 result of the covering of black sacks, the black cloth absorbing 

 the heat rays and lessening the loss of moisture from the fruit. 

 At least it is possible that the activity of the enzymes bringing 

 about ripening was checked or partially inhibited. 



Bioletti (3) has noted that European varieties of Vitis vinifera L. 

 do not ripen in parts of California precisely according to the theory 

 of Angot (i), who states that the buds of the European grapevine 

 commence activity when the mean daily temperature reaches 

 9 C. From this point until the ripening of the grapes, the sum 

 of the mean daily temperatures above o° C. must reach 1130 C. 

 for the earliest varieties, and 1520 C. for the latest. Bioletti 

 finds that under Californian conditions the actual dates of ripen- 

 ing are from 2 to 4 weeks later than the time estimated by Angot, 

 and that the greater delays in ripening are in the hotter localities. 

 For example, in the Coachella Valley the seasonal sum of temperature 

 above o° C. from February to November is 5728 F. Accordingly, 

 the grapes should ripen there from May 3 to May 23. As a matter 

 of fact, the earliest varieties ripen about May 15-30, and the 

 latest about June 15-30. Bioletti thinks that in these hottest 

 regions the temperature of maximum acceleration may be passed, 

 and intimates that the temperatures may become so high that a 

 retarding effect upon the ripening is exerted. 



