6oo SCIEXCE PROGRESS. 



evinced in many other ways, as Ewart's experiments, and 

 those of others, show. 



Examination of the third case mentioned above de- 

 monstrated that resistance to these poisons is lessened as 

 duration of exposure to their influence is lengthened. 



The question of the effect produced on seeds by depri- 

 vation of oxygen was the subject of an important communi- 

 cation by Romanes (19). The method adopted consisted 

 in sealing up seeds in vacuum-tubes of hig-h exhaustion, 

 in which they remained fifteen months ; in other cases, 

 after rest of three months in vacuo, seeds were transferred 

 to other tubes charged respectively with various gases at 

 the atmospheric pressure of the time of sealing. After a 

 further period of twelve months the seeds were sown. The 

 gases employed were carbon-dioxide and -monoxide, oxy- 

 gen, hydrogen, nitrogen, hydrogen-sulphide, water, ether, 

 chloroform. In all cases (with one exception) the seeds 

 were weighed individually, and seeds of equivalent weight 

 were taken from the same original packets as controls. The 

 results proved amply, that neither a vacuum of 1/1,000,000 

 of an atmosphere, nor any of the gases, exercised much, if 

 any effect on the ' vitality ' of the seeds. Gerniination was 

 in all cases perfectly normal. These experiments prove 

 conclusively that dormant seeds do not respire. 



Confirmation of Romanes' results are not wanting ; 

 similar ones have been obtained by De Candolle (2), 

 Jodin (5) and Ewart (9) as regards the effect of depriva- 

 tion of oxygen. The first enclosed seeds in a capsule of 

 metallic foil, to which a wire of platinum was attached ; the 

 capsule was plunged under mercury, and frequently agitated 

 to remove bubbles of air adherent to the seeds. If 

 respiration occurred, it could be only due to air contained 

 in the seeds before immersion. The results of four experi- 

 ments showed that this treatment did not affect the 'vitality' 

 of the seeds. In two of Jodin's experiments seeds were 

 introduced into a bent receiver full of air, which was inverted 

 under mercury ; the whole was kept in a dark cupboard, in 

 one case for four years, seven months and six days, in the 

 other for three years and seven months. The air was then 



