1909.] 



Latent Life of Resting Seeds. 



439 



Comparing the preceding tables it is seen that a feeble respiratory activity 

 is shown by some of the seeds examined in the ordinary stored condition, 

 which varies according to the seed and to the amount of moisture it contains. 

 Oats, hemp, barley, Eucalyptus, and Kicinus showed no evolution of carbon 

 dioxide, and the trace of oxygen absorbed may be the result of chemical oxida- 

 tion or physical absorption. 



Respiration was surprisingly active in the fresh wheat as obtained from the 

 seedsman, although not more than 1/300 part of what it is in an active 

 seedling. Further, the evolution of carbon dioxide ceased after a comparatively 

 small degree of desiccation. Eeference to the moisture tables shows that 

 the percentage of moisture contained by the wheat was not relatively large as 

 compared with the other seeds employed. 



As might be expected from the fact that the seeds of Acacia melanoxylon are 

 completely covered by a cuticle, which in the fully dried seed can withstand 

 nearly 45 minutes' immersion in strong sulphuric acid without becoming 

 permeable to water, the percentage of moisture eliminated by slow desiccation 

 in dry heat is less marked than in any of the other varieties of seeds. The 

 carbon dioxide evolved from the air dried seeds does not amount to 1/10000 

 of the amount evolved from an active seedling, and is, in fact, nearly within 

 the limit of error, and may possibly be the result of oxidations taking place 

 in the arillar appendages of the seeds. 



In any case, all respiratory activity as evidenced by the gaseous exchanges 

 completely ceased after the same seeds had been desiccated at 45° C. for 

 seven or eight days. For purposes of control various dead seeds, fragments 

 of dead wood, etc., were similarly tested in the air dry condition. In no 

 case could any sign of an evolution of carbon dioxide be detected, and the fact 

 that in some cases a trace of oxygen disappeared is not surprising, considering 

 the structure of the materials tested, and their large bulk relatively to the 

 amount of the enclosed air. 



The above results indicate that respiration is not a function of completely 

 dry seeds, nor even of seeds after a mild degree of drying, for only in one 

 isolated instance, that of Zea mais, was there the faintest trace of any apparent 

 respiratory activity present after remaining at 45° C. for one week. The 

 amount of carbon dioxide produced in this case was less than one-millionth 

 of that produced by an active seedling in the same time, and was evidently 

 the result of the slow outward diffusion from the bulky seeds of carbon 

 dioxide formed while in the air dry condition. The same applies to the traces 

 of oxygen absorbed, as the gaseous relationships inside and outside the seed 

 become equalised. 



This is made even more evident by the fact that the greater number of, the 



2 K 2 



