DORMANCY IN SEEDS 



115 



59° F) , and greenhouse temperatures for 2, 2}/^, and 3 months, and then 

 transferred back to greenhouse temperatures and photographed after three 

 weeks and seven weeks. Examination of this figure shows that 5° C (41° F) 



Figure 44. Tree jx-ony seedlings, one year and seven weeks after transfer to green- 

 house at 13° C (55° F) following a pretreatment of two and one-half months. Kept in 

 board-covered cold frame over winter. 



is the best temperature used for after-ripening the epicotyls. This tem- 

 perature gave a good epicotyl growth after 2 months of low temperature, 

 followed by greenhouse temperature. There was somewhat less growth 

 from the 10° C (50° F) exposure and still less at 1° C (34° F) exposure for 

 2 months. With 23^ and 3 months' exposure 1° C (34° F) and 10° C (50° F) 

 were only slightly less effective than 5° C (41° F). The exposure at 15° C 

 (59° F) gave little after-ripening of the epicotyl and the control at 20° C 

 (68° F) gave none. Fig. 44 shows some of the seedlings in Fig. 43B after 

 an additional year's growth. Fig. 45 shows the seedling production by 



Figure 45. Seedling production of tree peony in May 1933 from seeds planted in 

 flats which were placed in a board-covered cold frame. Seeds planted: A, Dec. 1931; 

 B, Feb. 1932; C, March 1932; D, May 1932; and E, July 1932. 



