UNIVERSITY OF CALIFORNIA PUBLICATIONS 



IN 



AGRICULTURAL SCIENCES 



Vol. 3, No. 11, pp. 283-368, plates 25-42, 9 text figures April 4, 1919 



AN INVESTIGATION OF THE ABNORMAL 



SHEDDING OF YOUNG FRUITS OF THE 



WASHINGTON NAVEL ORANGE* 



BY 



J. ELIOT COIT and ROBERT W. HODGSON 



Introduction 



The genus Citrus is undoubtedly of tropical origin. Alphonse de 

 Candolle. after much investigation of historical and philological data, 

 concludes that the feral range of the sweet orange is South China, 

 Cochin China, Java, and Sumatra, with a possible extension into India, 

 which regions are classed ecologically as tropical rain forest. Morpho- 

 logical evidence of the tropical origin of the orange is abundant, its 

 tropical mesophytic nature being indicated by glossy, broad, flat leaves 

 of rather loose and open cell structure, long life of leaves, absence of 

 stomatal devices for regulating transpiration, lack of root hairs, and 

 lack of a regular and non-interruptable period of dormancy. Living- 

 ston 1 has recently pointed out that the most efficient climate for plant 

 growth in the United States is peninsular or tropical Florida. The 

 significance of this is apparent when Ave remember that tropical 

 Florida is the only place in the United States where the orange has 

 run wild and been able so to maintain itself. In all countries where 

 the sweet orange has run wild after having been introduced into the 

 New "World, such as Brazil, Paraguay, northern Argentina, and to 

 some extent in Florida, the climate is distinctly tropical. 



Horticulturists have called attention to the fact that an environ- 

 mental complex which is most efficient as regards plant growth does 

 not necessarily conduce to the production of fruit of high commercial 

 value. On the other hand, some climatic factors, such as light and beat. 





•■ 



* Manuscript submitted January 17, 1918. 

 i Physiol. Res., vol. 1, April, 1916. 



