SEASONAL PHENOMENA IN THE LIFE OF PLANTS 463 



also accounts for the fact that unripe seeds of many weeds 

 germinate better and more rapidly than ripe ones. The ready 

 germination of immature seeds, which normally pass through a 

 period of rest, as for instance the seeds of winter wheat, is prob- 

 ably due to the fact that they are in a condition of preliminary 

 rest, which is more readily disturbed than a deep rest. 



General References 



Chandler, W. H. et al. Chilling requirements for opening of buds on 



deciduous orchard trees and some other plants in California. Calif. 



Agr. Exp. Sta. Bull. 611, 1937. 

 CoFFMAN, F. A. The minimum temperature of the germination of seeds. 



Jour. Am. Soc. Agron., 15: 257-270, 1923. 

 Crocker, W. Mechanics of dormancy in seeds. Am. Jour. Botany, 3: 



19-120, 1916. 



and L. V. Barton. After ripening, germination and storage of 



certain rosaceous seeds. Boyce Thompson Inst. Contr., 3 : 385-404, 1931. 



Denny, F. E., and L. P. Miller. Further experiments on shortening the 

 rest period of potato tubers. Boyce Thompson Inst. Contr., 7 : 157-187, 



1935. 



and . Storage temperatures and chemical treatments for 



shortening the rest period of small corms and cormels of gladiolus. 

 Boyce Thompson Inst. Contr., 7: 257-265, 1935. 



and E. N. Stanton. Localization of response of woody tissues to 



chemical treatments that break the rest period. Am. Jour. Botany, 15 : 



337-344, 1928. 

 EcKERSON, S. A physiological and chemical study of after-ripening. 



Botan. Gaz., 55: 286-299, 1913. 

 Harrington, G. T. Use of alternating temperatures on the germination of 



seeds. Jour. Agr. Res., 23: 295-332, 1923. 

 Knudson, L. Nonsymbiotic germination of orchid seeds. Botan. Gaz., 



73 : 1-25, 1922. 

 Laurie, A., and L. C. Chadwick. ''The Modern Nursery," Chap. IX. 



The Macmillan Company, New York. 1931. 

 Murneek, a. E., and J. C. Logan. Autumnal migration of nitrogen and 



carbohydrates in the apple tree, with special reference to leaves. Mo. 



Agr. Exp. Sta. Res. Bull. 171, 1932. 

 Shull, C. a. The role of oxygen in germination. Botan. Gaz., 52 : 64-69, 



1914. 

 and W. B. Davis. Delayed germination and catalase activity in 



Xanthium. Botan. Gaz., 75: 268-281, 1923. 

 Stiles, W. '*An Introduction to the Principles of Plant Physiology," 



Chap. XVII. Methuen & Co., Ltd., London. 1936. 

 Vacha, G. a., and R. B. Harvey. The use of ethylene, propylene and 



similar compounds in breaking the rest periods of tubers, bulbs, cuttings 



and seeds. PUnt Physiol, 2 : 187-195, 1927. 



