METABOLIC PROCESSES IN THE PLANT. 281 



107. The Behaviour of Plants in Contact with Nitrous Oxide Gas. 



It has often been asserted that plant-cells are able to utilise the 

 < ).vyiren of Nitrous oxide for normal respiration. I have made 

 this question the subject of special investigation, 1 and my experi- 

 ments have been made as follows. A retort-like vessel (see Fig. 11) 

 of about 90 c.c. capacity was filled with distilled water which had 

 been well boiled and then allowed to cool completely in a closed 

 vessel, and the water was then displaced by Nitrous oxide, a. 

 A second retort, 6, was similarly filled with boiled-out water, 

 which was replaced by N 2 O after the introduction of twenty seven - 

 days-old pea seedlings raised in the dark. A third retort, c, was 

 likewise supplied with pea seedlings and water, but the water was 

 displaced by atmospheric air. The N 2 is prepared by heating 

 commercial Ammonium nitrate in a retort, and the evolved gas is 

 led before use through a solution of Ferrous sulphate, and through 

 potash, to free it from the small quantities of Nitric oxide and 

 Xitric acid which may be present. In introducing the gas, care 

 must be taken that a very small quantity of water is left behind in 

 the tube of the retorts. In my experiments the retorts were left 

 for twenty hours at a temperature of about 20 C. The retort tubes 

 dipped into mercury, and the small quantities of water left in the 

 tubes served to protect the seedlings from the injurious effect of 

 the mercury vapour. At the end of the twenty hours all the 

 retorts were placed, still inverted, with their mouths under water 

 cooled by means of broken ice, care being taken not to admit air 

 during the transference. The gas present in the retorts a and 

 I) now gradually became almost completely absorbed, while in 

 the retort c a large volume of gas remained behind. The N 2 O 

 therefore could not have been decomposed by the seedlings. The 

 small quantities of gas remaining, after the absorption of N 2 0, in 

 the retort a (seedlings absent), and in the retort Z> (seedlings 

 present), were clearly derived from the water used for absorption.* 



We further make the following experiment to show that seeds 

 are unable to germinate in Nitrous oxide gas. Two retort-like 

 vessels, a and b, are filled with distilled water, which has been 



* The preparation of the N 2 must of course be allowed to proceed for some 

 time before the gas is introduced into the vessels, so as to drive all the air out 

 of the generating apparatus. At the close of the experiments we may transfer 

 the vessels to cold alcohol instead of cold water, since the former absorbs the 

 N.,0 more energetically. 



