iqiq] 



ROSE— AFTER-RIPENING AND GERMINATION 



289 



was made, as the experiment was used primarily for a different 

 purpose. Approximately 1000 seeds of each of the 2 crops, stored 

 under the same conditions as those indicated in table IV, showed no 



TABLE IV 

 Seeds of Tilia stored at o-2°C. for 140 days; then at io-i2°C. 



germination after 140 days at a low temperature. When brought 

 to the higher temperature the 191 6 seeds germinated vigorously and 

 in large numbers for the first 12 days and until the hj-pocotyls were 

 2-3 cm. long. From this point on no development took place and 

 the seedlings gradually died. Here a temperature of 10-12° C. 

 seems to be too low for continued growth. The 191 7 seeds ger- 

 minated much less vigorously, in fewer numbers, and only a few 

 developed hj-pocotyls 2 cm. long. Comparing the results obtained 

 in 1916 with those obtained in 191 7, it is seen that the seeds after- 

 ripen and germinate at temperatures slightly above freezing. 

 Davis and Rose (7) working with Crataegus found that after- 

 ripening takes place most rapidly at 3-6° C, and that temperatures 

 considerably higher are more favorable for germination and growth. 

 At 0-2° C. Tilia seeds after-ripen but do not germinate. At 

 4-6° C. after-ripening and germination both take place, the latter 

 taking considerable time. After-ripened seeds germinate poorly 

 at room temperature. Once germination has begun at the low 

 temperature, growth is best at temperatures above 12° C. The 

 germination of Tilia seeds depends, therefore, upon the proper 

 regulation of the temperature, and can be accomplished by a period 

 of after-ripening in moist storage at 0-2° C, followed by a sojourn 

 of 2 or 3 weeks at 10-12° C. until germination is well under way, 



