622 Mr. F. Kidd. The Controlling Influence of 



germinations were obtained with seeds sealed in air in the proportion 

 mentioned against nil with seeds kept in commercial packing, nil with 

 seeds kept in open air, and nil with seeds sealed in nitrogen.* 



In the foregoing experiments it will be observed that large seeds enclosed 

 in permeable seed coats and sealed with a definite proportion of air in an 

 impenetrable outer envelope were being dealt with. In these conditions, 

 where the life processes of the seeds resulted in the creation in the flask 

 of a partial pressure of C0 2 of 40-45 per cent, the vitality of the seeds 

 was markedly prolonged. 



A conclusion which Becquerel reaches, as the result of his researches, is 

 that in all cases of longevity in dry seeds the testas are exceptionally 

 strong and impermeable. The problem of the dry seed enclosed in an 

 impermeable or almost impermeable testa has certain striking affinities — 

 in that gaseous exchange in either direction is hindered or prevented — to 

 that of the wet seed, though in apparently good germinating conditions, 

 which does not germinate. But with the former problem we are not at 

 present directly concerned in this research. 



Section VI. — Biological Importance of Dormancy in Moist Seeds. 



The seed is a comparatively late arrival in geological time, and the 

 perfecting of its function has of necessity been a great point in the struggle 

 for existence amongst plants. A leading cause in the success of the 

 Angiosperms, as Prof. Seward has pointed out, has consisted in the 

 efficiency of the arrangements for nursing the embryo. There can be no 

 doubt that a ruling factor in this efficiency has been the adjustment of 

 all the life processes of the moist resting seed to the end of attaining a 

 fit time for germination. It is suggested by these experiments that the 

 presence of carbon dioxide in the tissues of the embryo acting as a 

 restraining and inhibiting agent on the life processes of the seed, and as 

 a dominant factor in relation to the oxygen stimulus, has been utilised 

 in attaining this efficiency of the latent seed for which fit conditions of 

 germination have not yet arrived. The various structures of the testa and 

 its behaviour under different conditions in regulating the gaseous exchanges 



* The favourable results obtained in these experiments in prolonging the vitality of 

 these rapidly deteriorating seeds were greatly in excess of those which are secured by 

 present commercial methods of packing for transport and import. In experiments on a 

 large scale the seeds might be simply sealed (in the proportions of air mentioned) in large 

 carboys, such as are used for the transport of distilled water, covered with wicker or wire 

 netting. In case of too high an internal pressure, arising from overfilling with seeds, a 

 simple form of safety valve might be inserted in the sealing. 



