Influence of very Low Temperatures on Germinative Power. 16i 



the above gases or vapours, exercised much, if any, effect on the sub- 

 sequent germinative power of the seeds employed. 



These experiments of Romanes are certainly of the highest im- 

 portance, since the seeds were submitted for a long period to condi- 

 tions which must certainly have excluded anything like respiration 

 by ordinary gaseous exchange, but the conditions did not preclude 

 with the same certainty the possibility of chemical interactions of some 

 kind or other within the protoplasm, those ill-understood changes, in 

 fact, which have been referred to " intramolecular respiration." It 

 is true that in some of the experiments, notably those in which the 

 vapours of chloroform and ether were employed, the probability of 

 any such internal reactions is rendered somewhat remote, but still, 

 in most cases, the experiments admit of the possibility of feeble 

 metabolic activity continuing in the cytoplasm. 



It occurred to us, some months ago, that more evidence would 

 probably be forthcoming on these points if we could submit seeds to 

 a temperature below that at which ordinary chemical reactions take 

 place, thus eliminating any possibility of interactions between the 

 constituents of the protoplasm. 



Owing to the kindness of Professor Dewar, who has been good 

 -enough to place the resources of his laboratory at our disposal, and 

 to undertake this part of the work for us, we have been able to 

 •ascertain how far the subsequent germinative power of a consider- 

 able variety of seeds is affected by prolonged exposure to the very 

 low temperatures produced by the slow evaporation of liquid air. 



The seeds, enclosed in thin glass tubes, were slowly cooled, and 

 immersed in a vacuum-jacketted flask containing about 2 litres of the 

 liquid air, which was kept replenished so as to submit the seeds for 

 110 consecutive hours to a temperature of from —183° C. to 

 — 192° C. About 10 litres of liquid air were required for the experi- 

 ment. 



The seeds had been previously air-dried only, so contained from 

 about 10 to 12 per cent, of natural moisture. After the above treat- 

 ment they were slowly and carefully thawed, a process which occupied 

 about 50 hours, and their germinative power was then compared 

 with control experiments made on other portions of the seed which 

 had not been treated in any way. 



The seeds experimented on were as follows : — 



Hordeum distichon. 

 Avena sativa. 

 Cucurhita Pejoo. 

 Cyclanthera exjplodens. 

 Lotus Tetragonolobus. 



Trigonella foenum-grcecum. 

 Impatiens balsamina. 

 Helianthus annuus. 

 Heracleum villosum. 

 Convolvulus tricolor. 



Pi sum elatius. I Funhia sieboldiana. 



