REST PERIOD STUDIES WITH SEEDS 57 



the seeds of many plants such as the willows, soft maple, etc.., germi- 

 nated immediately, but others, such as the ash and hornbeam, did not 

 germinate until the following year. In the case of many trees and 

 shrubs maturing their seed early in the season, it was thought that 

 germination must proceed immediately or the seeds would be destroyed. 



It has long been known that in the case of some paired seeds, such 

 as the cocklebur, both seeds do not usually germinate the same season. 

 Arthur, 2 who made the first careful study of Xanthium, reported that 

 generally the germination of one kernel in the bur was delayed, but 

 that in some cases both may germinate the same season. Shull 3 

 (1911) in further investigations with Xanthium found that the mini- 

 mum oxygen requirement for the germination of the seed from this 

 plant was abnormally high, and also that the minimum for the two 

 seeds differed. This explained the delay in germination and also the 

 irregularities in the delayed growth. 



Beal 4 ( 1910) gives some interesting data concerning the vitality 

 of buried seeds and incidentally raises some questions concerning their 

 germinating capacities. Eight or nine species out of twenty-two 

 germinated even after they had been buried thirty years. In speaking 

 of his results, Beal says : "I have never felt certain that I had induced 

 all the sound seed to germinate. I moisten the sand containing the 

 seeds and forthwith a goodly number germinate, and then they come 

 straggling along. I dry the soil and wait a few weeks, and after 

 moistening, in a few days, or few months, more seed germinate. Why 

 was I unable to induce them to start, when treated to various degrees 

 of temperature and moisture, for several months?" 



2. Arthur, Proc. Soc. Prom. Agr. Sc., 16, p. 70. 



3. Shull, Bot. Gazette, 52, pp. 453-77. 



4. Beal, Proc. Soc. Prom. Agr. Sc. 31, pp. 21-23. 



