REPRODUCTIVENESS AND SEED GERMINATION 395 



6. Low temperatures favor flowering and seed formation, while high tem- 

 peratures favor vegetativeness in the celery (Thompson) and cabbage (Miller). 

 How can this be reconciled with the work of Kraus and Kraybill? 



7. Bakhuyzen (1924) reported that blooming of wheat occurs when the 

 ratio of water to dry substance falls to a certain point. Can this be reconciled 

 with the results of the work on the C/N ratio? 



8. Chinese Imperial rice flowered in 72 days when exposed to 7 hours of 

 light daily, but blossomed in 106 days of 12 hours daylight each. Is it a "short" 

 or a "long" day plant? 



9. Would you expect the germination of forest tree seed to be favored 

 by light or by darkness? Why? 



10. The temperature coefficient of absorption of water by Xanthium and 

 Pisum seed and by the grains of Zea mays between 5 and 50° C. is about 1.5 

 (Shull). What are the common names of these plants and what does the state- 

 ment mean? 



11. Lumiere reported that extracts from dead leaves hindered germina- 

 tion of seeds, and offered this as an explanation of the fact that many seeds 

 would not germinate in the fall. Outline a simple method of testing this 

 hypothesis. 



12. Guillaumin (1923) found that seed would keep longer in the dark in 

 a vacuum than in ordinary air in the light. Give reasons for this. 



13. Would you expect plants which thrive and set seeds in high latitudes, 

 e. g., oats, to be "long" or "short" day plants? Why? 



14. Many plants from the temperate zone will not blossom when trans- 

 planted to the tropics. Can you suggest any reasons for this? 



15. It was stated in the text that Salix pierotii seeds retained their viability 

 longer when kept in the cold over sulphuric acid. What is the function of the 

 sulphuric acid? 



16. How does one test the catalase activity of a substance? 



REFERENCES 



Coffman, F. — The minimum temperature of the germination of seeds. Jour. 



Am. Soc. Agron., 15:257, 1923. 

 Crocker, W., and Barton, L. V. — After ripening, germination, and storage 



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

 Darlington, H. T. — The fifty year period for Dr. Beal's seed viability ex- 

 periment. Am. Jour. Bot., 18:262, 1931. 

 Davis, W. E. — Primary dormancy, after ripening, and the development of 



secondary dormancy in embryos of Ambrosia trifida. Am. Jour. Bot., 



17:58, 1930. 

 Deats, M. E. — The effect on plants of the increase and decrease of the period 



of illumination over that of the normal day period. Am. Jour. Bot., 



12:384, 1925. 

 Dorsey, M. — Relation of weather to fruitfulness in the plum. J. Ag. Res., 



17:103, 1919. 

 Gardner, W. — Effect of light on the germination of light sensitive seeds. 



Bot.Gaz., 71:249, 1929. 



