Influence of very Low Temperatures on Germinative Power. 163 



fully whether we must regard the life of the resting seed as com- 

 pletely arrested for a time or merely temporarily slackened (ralentie), 

 and he giyes the results of some new experiments on seeds maintained 

 at from —37° C. to —53° C. in the " snow-box " of a refrigerating* 

 machine for a period of 118 days. Most of the seeds resisted this 

 treatment successfully, and the author concludes that after a suffi- 

 cient interval of time has elapsed the protoplasm of the ripe seed 

 passes into a state of complete inertness in which it is incapable 

 either of respiration or assimilation, and that whilst in this condition 

 it can support, without detriment to its subsequent revival, rapid 

 and considerable lowering of temperature. 



De Candolle then points out that if it really be a fact that the 

 suspended life of a resting seed is in any way dependent on respira- 

 tion, we might expect this to be shown by submitting seeds to a 

 barometric vacuum for some time. He does not appear to have 

 followed out this suggestion, and is apparently unaware of the direct 

 experiments on this point carried out by Romanes two years pre- 

 viously ; he argues, however, that if ordinary respiration is a factor 

 of any importance, this may be determined by immersing the seeds 

 in mercury for such a length of time as to ensure the complete con- 

 sumption of the small amount of oxygen contained within their 

 tissues. It was found that when seeds of wheat, and of Lepidium 

 sativum were thus treated, for periods varying from one to three 

 months, their power of germination was not sensibly affected. 



Although these last described experiments of C. de Candolle go 

 far to show that any considerable amount of respiration is unnecessary 

 for the maintenance of potential life in the protoplasm of resting 

 seeds, they are not inconsistent with the view that some minute 

 amount of gaseous exchange may be going on during the whole 

 course of the experiment at the expense of the oxygen contained in 

 the seeds at the time of immersion in the mercury. The results 

 would have been far more conclusive on this point if it had been 

 shown that the gaseous oxygen originally contained in the seed 

 tissue had been completely used up in an early stage of the experi- 

 ment. The experiments of Romanes, however, conducted with high 

 vacua and atmospheres of various gases, leave no room for doubt on 

 this question, and we must consequently abandon all idea of the 

 dormant state of resting seeds having any necessary dependence 

 whatever on ordinary respiratory processes. Neither set of experi- 

 ments, however, excludes the possibility of molecular interchanges 

 in the protoplasm itself, such molecular transpositions in fact as those 

 which can often be induced in living cells placed under anaerobic 

 conditions, and which are all exothermic in character, and generally, 

 but not necessarily, attended with the liberation of more or less C0 2 . 

 The great value of the low temperature experiments we have described 



