1909.] 



Latent Life of Resting Seeds. 



441 



no otherwise non-germinable seeds could be excited to germination by the 

 addition of any kind of enzyme, and where the germination was feeble the 

 addition of enzymes usually lowered the percentage germination and often 

 delayed germination also to some extent. 



The erepsin appears to be more abundant than the pepsin, but otherwise in 

 the cases of all three ferments greater differences are shown between 

 different samples of the same age than between different seeds, or between 

 the same seeds of varying ages. Pepsin appears, however, to be more 

 abundant in rye than in any other cereal, and is almost absent from maize. 

 Dry oats, barley, and wheat can in part resist a temperature of 99° to 100° C. 

 for 1 to 4-|- hours ; after 6 hours' exposure all are killed, but the ferments are 

 apparently unaffected. All the ferments are destroyed after an hour's dry 

 heat at 130° to 131° C. The pepsin appeared to be least (1 hour at 124° C), 

 the erepsin more (1 hour at 124° to 128° C), and the diastase, especially of 

 barley, most resistant to diy heat (1 hour at 124° to 131° C). 



Two days' exposure to liquid air, although it delays the subsequent 

 germination and may also decrease the percentage, does not absolutely destroy 

 any of the seeds tested and does not appreciably affect tbe ferments in any of 

 the cereals. The dry diastase of barley is therefore able to withstand a range 

 of temperature of —200° to +130° C. It is therefore thermally a highly 

 stable chemical compound. 



Many seeds, including all cereals, give off appreciable quantities of carbon 

 dioxide when stored in the air dried condition, but others show no signs of 

 respiration whatever. The respiration of air dried wheat is especially pro- 

 nounced, but in practically all cases every sign of respiration ceases when the 

 seeds are moderately desiccated, although in the case of large seeds like 

 maize minute traces of carbon dioxide may continue to escape for a time. 



SPECIAL BIBLIOGRAPHY. 



Vines, " Proteolytic Enzymes in Plants," ' Annals of Botany ' : — 

 (i) Vol. 17. pp. 237—264. 

 (ii) Vol. 17, pp. 597—616. 

 " The Proteases of Plants " :— 

 (i) Vol. 18, pp. 289—317. 

 (ii) VoL 19, pp. 149—162. 



(iii) Vol. 19, pp. 171—187. 



(iv) Vol. 20, pp. 113—122. 

 Vol. 22, pp. 103—114. 



J. W. T. Duvel, "The Vitality and Germination of Seeds," U.S. Department of 



Agriculture, Bureau of Plant Industry, Bull. No. 58. 

 Dr. G. Albo, " Les Enzymes et la Faculte . Germinative des Graines," ' Archives des 



Sciences Physiques et Naturelles,' Cent-treizieme annee, vol. 25 ; " La Vita dei 



