450 PLANT PHYSIOLOGY 



composition of the fat changes considerably. According to the 

 investigations of S. L. Ivanov, a certain variety of flax gave 

 in the Moscow region excellent drying oil due to a high content 

 of the more unsaturated fatty acids, containing three double 

 bonds such as linolenic acid, while in Turkestan the same variety 

 produced oil with a prevalence of less unsaturated acids, yielding 

 a poor drying oil. If during ripening of the seeds there prevail 

 lower temperatures with alternation between the day and night 

 temperatures, then mostly unsaturated acids are formed. But 

 on the contrary, if ripening occurs at higher and more uniform 

 temperatures, more saturated acids are produced. Mountain 

 regions are similar to northern regions in their effect upon oil 

 plants. Hence, the practical conclusion may be drawn that the 

 best varieties of drying oil are obtained from oil seeds either of 

 northern or of high mountain origin. 



Climatic conditions also exert a great influence upon the 

 ripening of succulent fruits, temperature being Ukewise the chief 

 factor. With low temperatures and a prevalence of cloudy 

 weather, which reduces the heating of the fruit by direct sunrays, 

 they ripen slower and contain more acids and tannins and less 

 sugars. Conversely, in a warm and sunny climate, the fruit 

 produced is richer in sugars. But, of course, varietal differences 

 in the chemical composition are of great significance in this 

 respect. 



General References 



Allen, F. W. Physical and chemical changes in the ripening of deciduous 



fruits. Hilgardia, 6: 381-441, 1932. 

 Archbold, H. K. Chemical studies in the physiology of apples, XII. 



Ripening processes in the apple and the relation of time of gathering 



to the chemical changes in cold storage. Ann. Botany, 46: 407-459, 



1932. 

 Brink, R. A. The physiology of pollen. Am. Jour. Botany, 11 : 218-228, 



283-294, 351-364, 417-436, 1924. 

 BucHOLZ, J. T., and A. F. Blakeslee. Pollen-tube behavior with reference 



to sterility in Datura. N. Y. Hort. Soc. Mem., 3: 245-260, 1926. 

 Crane, M. B., and W. J. C. Lawrence. ''The Genetics of Garden Plants." 



Macmillan & Company, Ltd., London. 1934. 

 Dorset, M. J. A study of sterility of the plum. Genetics, 4 : 417-484, 1919. 

 Edwards, T. I. Relations of germinating soybeans to temperature and 



length of incubation period. Plant Physiol., 9: 1-30, 1934. 

 Florin, R. Pollen production and incompatibilities in apples and pears. 



N. Y. Hort. Soc. Mem., 3: 87-118, 1926. 



