DORMANCY IN SEEDS 



113 



Dormant Epicotyls. At the Institute we have found a number of seeds in 

 which the epicotyl has to be after-ripened by a period of low-temperature 

 exposure after the radical and hypocotyl have grown. Table 14 shows the 

 seeds studied to date that belong to this group. In all of these the germi- 

 nation and formation of the root system — a process that takes place at 



Table 14. Effective Treatment for Producing Plants from Seeds with Dormant 



Epicotyls. 



* Daily alternation. 



higher temperatures — is rather slow, requiring from two to three months 

 in the herbaceous peony and Viburnum Opulus, to 6 to 17 months in 

 V. acerifolium and V. dentatum. One might expect low-temperature strati- 

 fication of the seeds to hasten the growth of the root system, but such 

 has not proved to be the case. It is evident that there ought to be some 

 way of getting more prompt root production in this type of seed, but it 

 has not been discovered to date. In some of these seeds the percentage of 

 germination is also low. All these seeds will produce some seedlings the 

 second spring if the seeds are properly planted early in the spring. The 

 tree and herbaceous peonies and V. Opulus will give a good stand of seed- 

 lings the second spring if planted in late spring or early summer. Some of 

 the seeds of forms like V. acerifolium, V. dentatum, V. dilatatum, and 

 V. prunifolium are likely to carry over to the third spring or later for 

 complete seedling production. With the conditions met in nature, which 

 are generally far from the optimum, seedling production in all these may 

 extend over several years. 



Fig. 43 shows the behavior of tree peony seedlings ^ with hypocotyls 

 1 to 3 cm planted in pots and placed at 1°, 5°, 10°, 15° C (34°, 41°, 50°, 



