NURSERY PRACTICE FOR PRAIRIE-PLAIXS PLANTING 19 



Others, notably elm and depulped chokecherry seed, lose their 

 viability rapidly and will generally produce little or no germination at 

 the end of a year. Some success has been attained in maintaining a 

 fair degree of viability in American elm seed for 1 year by holding it 

 close to the freezing point after very carefid drying (34) ■ 



George (12) reports that thoroughly dried American elm seed was 

 successfully stored for 10.5 months in both open and closed containers. 

 These lots gave 77 and 79 percent germination respectively. 



Norman Devick, of the Forest Service, from a similar test at James- 

 town, X. Dak., reports 12.5 percent germination of American elm seed 

 stored dry for 11 months in burlap bags; 11 percent when stored in 

 sealed cans under the roof of a warehouse; and 26 percent in sealed 

 cans buried 1.5 feet underground. A portion of the first two lots was 

 dewinged by beating the sacks against a brick wall before placing the 

 seed in storage. Germination on the dewinged lots was 0.5 and 21.0 

 percent respectively for the burlap bags and sealed containers. It 

 appears that if stored seed is to be dewinged to facilitate machine 

 sowing, the dewinging process should be delayed until just before 

 sowing of the seed. 



E. i. Roe. of the Lake States station, has obtained a 67 percent 

 germination on seed of Siberian elm which had been thoroughly dried 

 and stored in airtight tin containers for 4 years at 41° F. 



Because of the fact that very few experiments have been made 

 which give a basis for an exact procedure in treating seeds, it is 

 necessary to fall back on general experience and to formulate some 

 general rules from a few cases in which the information is most 

 complete. 



Broadly speaking, the degree of drying which seed will tolerate, 

 and which in itself determines or at least indicates how long the 

 vitality will remain in seed, must be gaged by the characteristics of 

 the particular type of seed under natural conditions. Thus, seed 

 which fall to the ground as soon as ripe and either germinate imme- 

 diately (if early) or normally lie on sheltered ground or in litter, will 

 tolerate very little drying and will be difficult to preserve in a viable 

 condition. With possibly few exceptions among the drupaceous fruits 

 and berries, those forms which normally adhere to the tree well into 

 the winter, or in some cases much longer, are accustomed to being 

 severely dried and can be preserved. Longevity may, however, vary 

 from 2 to 50 years, the maximum period occurring only when an ideal 

 condition of storage has been found. 



The reason for this close relation between drying tolerance and 

 longevity is that all living seed respire, and in so doing consume the 

 foods which are within or immediately available to the "germ" or 

 embryo. Respiration can be checked to a very low point by dryness 

 and by low temperatures, and the consumption of vital foods be thus 

 slowed down; but it is not known with certainty whether this process 

 can be completely stopped without killing the embryo. The extent 

 to which drying can be safely employed depends on the protoplasm 

 within the germ cells. It is undoubtedly possible for certain forms of 

 protoplasm to be very severely dried without coagulation and death : 

 while other forms (as in young, growing tissues of nearly all plants 

 will not tolerate a low moisture content. 



A seed is a dormant form of a plant : but as in the case of the sleeping 

 or hibernating animal, this does not mean complete cessation of the 



