698 T ho day. — On the Effect of Chloroform on 
its direct effect will be of a relatively simple physical nature. 1 It is with 
the changes which follow the exposure of leaves to chloroform vapour that 
this paper is concerned. Miss Irving 2 has given numerous data for the rate 
of production of carbon dioxide by Barley shoots, and by leaves of Cherry 
Laurel under the influence of chloroform. In the experiments described 
here,, in which leaves of Cherry Laurel and certain other plants received 
similar treatment, the relation which the absorption of oxygen bears to the 
concurrent evolution of carbon dioxide was investigated. As the chemical 
nature of the material used in respiration alters the respiratory quotient, 
some leaves were first starved in the dark and then chloroformed. 
The work was begun during my tenure of a Mackinnon Research 
Studentship of the Royal Society in 1909-10, and carried out at the 
Cambridge Botany School. Tdesire to express my thanks to Dr. Blackman 
for his kind and helpful interest in the work. 
Method. 
In order to investigate absorption of oxygen as well as evolution of 
carbon dioxide, the procedure adopted was to analyse samples of the air of 
a closed chamber in which leaves were contained. It appeared desirable 
. to be able to examine the initial period of stimulation very closely, and for 
this purpose to take samples at relatively short intervals. As the change 
in the composition of the air in the respiration chamber during any given 
interval is smaller the shorter the interval, but depends also upon the total 
volume of air and on the quantity of respiring material, these factors had 
to be adjusted so that the changes could be measured with sufficient 
accuracy. 
The analyses were made with the capillary eudiometric apparatus of 
Bonnier and Mangin, of the form described by Aubert. 3 This has the two 
advantages that analyses can be made quickly, a valued feature when 
samples were to be taken at short intervals, and also that very small volumes 
can be analysed, and thus the diminution of the total volume of gas can 
without serious error be ignored. An account of the way in which this 
apparatus was used (which differed in some respects from Aubert’s instruc- 
tions), with a discussion of the sources of error, has been given separately. 4 
As the limit of error was found to be about 01 per cent, of the total 
volume of air analysed, 5 in determining the percentages of C 0 2 and 0 2 in 
1 Cf. H. E. and E. F. Armstrong, Roy. Soc. Proc., B, 82, 1910, pp. 588-602 ; Annals of Botany, 
xxv, 1911, p. 508; Bechold, Die Kolloide in Biologie u. Medizin, 1912, p. 32. 
2 Annals of Botany, xxv, 1911, p. 1077. 
8 Rev. gen. de Bot., iii, 1891. 4 Annals of Botany, xxvii, 1913, p. 565. 
5 In addition to a variation from the mean up to about +o-i % among a series of analyses of the 
same sample of air, the percentage of 0 2 was on the average 0.2 below the correct value, 20.9. 
This error has since been traced to its sources ; it does not vitiate the results, as it enters into all 
the analyses equally, and is eliminated when two results are subtracted in calculating the change of 
