Aug. 14, 1916 Agricultural Value of Impermeable Seeds 763 



belonging to the Malvaceae, atriplex {Atriplex spp.), of the Chenopodia- 

 ceae, alfilaria {Erodium cicutarium (L.) L/Her.), of the Geraniaceae, 

 asparagus {Asparagus officinalis L-), of the Convallariaceae, morning- 

 glory (Ipomea purpurea (L.) Lam.), of the Convolvulaceae, and canna 

 {Carina indica L.), of the Cannaceae. The cherry-tomato (Physalis 

 pubescens L.)» OI the Solanaceae, occasionally has some impermeable 

 seeds. 



LONGEVITY OF IMPERMEABLE SEEDS 



Although stating that some seeds with readily permeable coats may 

 retain their vitality for many years in dry air, Ewart (7) was inclined 

 to attribute extreme longevity of seeds in the soil exclusively to the 

 impermeability of the seed coats. In contrast to Hwart's conclusion the 

 work of Duvel, 1 Beal (1-5), and others indicates that great longevity 

 of seeds even in moist soil may sometimes be the result of factors entirely 

 independent of an impermeable seed coat. There is no doubt, however, 

 that the possession of such a seed coat contributes to the length of life 

 of the seed by decreasing or entirely preventing respiration and imbibi- 

 tion and, in general, by reducing the rapidity with which all physical 

 and chemical changes take place within the seed. The seeds which 

 Ewart (7) and Rees (17) have shown to retain their viability for 15 to 50 

 years or longer are almost exclusively seeds with impermeable seed coats. 

 Beal, however, found the seeds of some typically permeable seeds (for 

 example, Brassica nigra) viable after 30 years in the soil. 



Becquerel (6) has reported the germination of impermeable seeds of 

 three leguminous plants over 80 years old, and Ewart (7) mentions 

 several plants as germinating from 5 to 80 per cent when over 50 years 

 old. 



According to Ewart, the curves of viability based on the germinating 

 capacity of seeds of known age suggest 150 to 250 years as the probable 

 extreme longevity of any known seed. 



EXPERIMENTAL WORK DURING 1909-1916 



The major part of the work reported in this paper was done with the 

 seeds of red clover, alsike clover, white clover, white sweet clover, alfalfa, 

 hairy vetch {Vicia villosa Roth.), and okra. A small amount of work was 

 done also with seeds of crimson clover {Trifolium incarnatum L.), black 

 locust {Robinia pseudacacia L-), kidney bean {Phaseolus vulgaris L.), 

 garden and field peas {Pisum sativium L-), cowpeas, and Chamaecrista 

 nicitans L. Muench. 



Nearly all chamber tests and greenhouse tests were made with two 

 samples of 100 seeds each from each lot of seed tested. In some cases 

 the number available was small and less than 200 seeds were used. A 

 number of tests of okra were made with two lots of 50 seeds each. In the 



1 Unpublished data. 



