. TEMPERATURES OF SMALL FRUITS 183 



That fruits of all colors absorb considerable amounts of radiant 

 energy is highly probable if we accept Pfeffer's ( (7), p. 330) 

 estimate that green and other colored, leaves may absorb from 

 50% to 90% of the sun's rays falling upon them. 



SUMMARY 



Observations on a variety of small fruits show that on clear 

 days they usually have a temperature considerably above that 

 of the air. 



This rise in temperature seems to be mostly due to the absorp- 

 tion of radiant energy from the sun; no such difference was 

 found at night or on cloudy days, and berries in the shade are 

 uniformly cooler than those in the sun. 



No constant difference in the temperatures of fruits of the 

 same variety but of different colors has been demonstrated. 



LITERATURE CITED 



(1) AsKENASY, E. : Ueber die Temperatur welche Pflanzen im Sonnenlicht 



annehmen. Bot. Ztg. 33: 441-444. 1875. 



(2) DuTRocHET, M. : Recherches sur la chaleur propre des etres vivans k basse 



temperature. Ann. Sci. Nat. Bot., ter. 2, 13: 5-49, 65-85. 1840. 



(3) Ehlers, J. H.: The temperature of leaves of Pinus in winter. Amer. 



Jour. Bot. 2: 32-70, 4 fig., bibliography, 1915. 



(4) Ewart, a. J.: Effects of tropical insolation. Ann. Bot. 11: 439-480. 1897. 



(5) Franklin, H. J.: Report of the Cranberry Substation (Mass.) for 1916. 



Mass. Agri. Exp. Sta., Bull. No. 180. Nov. 1917. 



(6) Lamarck, J. B. P. de M de.: Flore fran^oise .... t. 3, Paris. 1778. 



(7) Pfeffer, W.: Physiology of plants .... v. 3, Oxford (Eng.). 1906. 



(8) Richards, H. M.: Evolution of heat by wounded plants. Ann. Bot., 11: 



29-63, 1897. 



(9) Rodewald, H.: Quantitative Untersuchungen iiber die Warme und 



Kohlensatireabgabe athmender Pflanzentheile. Jahrb. Wiss. Bot., 

 8: 263-245. 1887. 

 (10) Stevens, N. E., and Wilc3x, R. B. : Further studies on rots of strawberry 

 fruits. U. S. Dept. Agr. Bui. 686. June 24, 1918. 



