1912] DAVIS & ROSE— AFTER-RIPENING 6 1 



removed from the carpels 



and at a temperature of 5 or 6 



may 



months, and if the testas are removed 



embryos treated, the period may be reduced to 30 days. Tem- 

 peratures below o° C. are not favorable for after-ripening. Seeds 

 kept at —2 to — 3 C. did not after-ripen. Seeds at o° C. after- 

 ripened, but not so readily as those kept at a few degrees above 

 o C. The most favorable temperature for after-ripening seems to 

 be 5 °-6 



Low temperatures alternating with high temperatures 

 favorable for after-ripening. 



/ 



removed from the cold chamber 



j have passed through the after-ripening period and subjected to the 

 I temperature of the greenhouse, the high temperature either stops 

 V or greatly retards the process of after-ripening. 





I quickly. T 

 \ germination. 



ids are completely after-ripened and removed from 

 temperature of the greenhouse, they germinate a 

 le hierh temperature erreatlv stimulates the proces 



After-ripening readily takes place under ordinary oxygen pres- 



determined 



may be 



The pulp, carpels, and seed coat itself tend to delay the process 



by 



mbry 



known 



/ 



Seeds treated dry as well as those treated under water did not 

 after-ripen. 



While after-ripening and germination in the hawthorn is a 

 continuous process, that is, we cannot tell where one leaves off and 

 the other begins, the optimum temperature for the latter is con- 

 siderably above the optimum for the former. 



In conclusion, we wish to express our thanks to Dr. William 

 Crocker, at whose suggestion this work was undertaken and who 

 offered many valuable suggestions during its progress. 



The University of Chicago 



