22 THE NURSERY-MANUAL 



If seeds are buried in the ground and exposed to the action 

 of frost, the period of dormancy is usually considerably re- 

 duced. Thus Pammel and King report (Proc. Iowa Acad. 

 Sci. xv) experiments by Fawcett showing that "the dormant 

 period of common pigweed (Amarantus retroflexus) was nine and 

 one-third days when kept in packages in a dry room, and only 

 six and one-third days after having been wintered out of doors. 

 In the case of wild rye, the dormant period was lessened from 

 nine to five days . . . while the percentage of germination 

 was increased from 22 per cent to 48 per cent, and the pigweed 

 from 40 per cent to 50 per cent. In general, the longest dor- 

 mant period was found in those seeds which have the hardest 

 and thickest coats." 



The better germination of some kinds of seeds after being 

 subjected to freezing is the result of the cracking of the shell 

 and the letting in of moisture, rather than the lessening of an 

 inherent dormancy; perhaps this is always the explanation. 

 Plant-growers resort extensively to the burying of nuts and 

 hard-shelled seeds to insure germination. They also file or 

 notch certain seeds, as those of the moonflowers, to allow water 

 to enter and to start the germination processes, taking care, of 

 course, not to injure the embryo. 



How long germination may be delayed and the seeds still 

 remain viable (or germinable) depends on the kind of plant 

 more than on the conditions of storage. The longevity of 

 seeds, in other words, is largely an hereditary trait lying prob- 

 ably in the anatomy and chemical constitution. In this realm, 

 new experiments are needed on a considerable scale, reinforced 

 by the modern understanding of the physiological processes. 



The stories of live seeds being taken from the mummies of 

 ancient Egypt are not credible ; these statements have often 

 been exposed. Yet certain seeds may outlive a human life. 

 Pammel and King report the following table from Ewart, of 

 Victoria (Australia), on certain rather remarkable longevities: 



