TEMPERATURES OF SMALL FRUITS 181 



p.m. was 32°C., and of a box of yellow raspberries picked at 

 the same time on adjacent bushes of somewhat more luxurious 

 growth was 31°C. The air temperature at this time was 27°C. 



CRANBERRIES 



Observations on cranberries were made by one of the writers 

 while working in cooperation with Dr. H. J. Franklin, Superin- 

 tendent of the jNIassachusetts Cranberry Station at East Ware- 

 ham, and were published by Dr. Franklin in his Annual Report 

 for 1916 (5). These data first called attention to the fact that 

 the temperature of berries when picked is frequently above 

 that of the air, and were the starting point of the observations 

 presented in the present paper. 



RELATION OF TEMPERATURE TO SUNSHINE 



The facts indicate that the higher temperature of the fruits is 

 largely due to the absorption of radiant energy. In general the 

 difference between the tem.perature of the berries and that of 

 the surrounding air was greatest when the sun was highest, less 

 in the forenoon and afternoon, and practically zero at night and 

 on cloudy days (see table 1). Exceptions occurred in those 

 cases when the temperature of the air dropped rapidly and that 

 of the fruit had not yet adjusted itself. No constant difference 

 between the temperature of the berries and that of the surround- 

 ing air, at night or on cloudy days, was ascertainable by the 

 methods used.^ The temperature of berries borne in the shade 

 was much lower when picked than was that of similar berries 

 exposed to the sun. Currants and gooseberries which had been 

 exposed to the direct rays of the sun for some time acquired a 

 higher temperature than those which were on the bushes in 

 partial shade. 



5 This does not mean that berries when not exposed to the sun arc always at ex- 

 actly the same temperature as the air. Their temperature is undoubtedly some- 

 what affected by respiration and the temperature of the berries ordinarily lags 

 somewhat as that of the air changes. Especially in the morning, when the air is 

 becoming rapidly warmer, there is often a period when the berries are markedly 

 below air temperature, sometimes 4 to 5 degrees C. This period is longest on 

 mornings when the berries are wet with dew. 



