1091 
upon Respiration and Assimilation . 
appearance of the red colour noted. It was found that at temperatures 
between 35 0 and 55 0 C. the presence of HCN became evident in 50-60 seconds, 
while at 30°C. two minutes elapsed, and at n°C. quite twenty minutes. 
Some observations on the effect of partial or complete removal of the 
water from leaves were also made. A fresh Cherry Laurel leaf in chloro¬ 
form vapour will turn brown and evolve HCN in about half an hour, but 
the more the water is removed by allowing the leaf to dry up in the air the 
longer the time required for these signs, which seem to go closely together. 
The following times were found :— 
Leaf dried to 90 % of fresh weight—brown in 1 hour 
33 
,, 80 / ,, 
3) 
33 
6 hours 
33 
75 1 ° >> 
3* 
33 
26 „ 
33 
5 ) 7 2 ^ » 
J) 
33 
30 „ 
33 
„ 5 ° % 
33 
33 
36 „ 
A leaf completely air-dry retained its green colour indefinitely in chloroform 
vapour and also evolved no trace of HCN. 
PART II. 
The Effect of Chloroform upon Assimilation in 
Prunus Laurocerasus. 
Several observers, Claude Bernard, 1 Bonnier, 2 Ewart, 3 have brought 
forward evidence that the process of photosynthesis in plants is arrested 
by chloroform, but there has been no systematic study of the action of 
different doses, except that of Kegel. 4 Kegel, who worked with water 
plants, concluded that chloroform under certain conditions increases the 
evolution of oxygen, while mostly it depresses it. His evidence for the 
acceleration of assimilation is not very convincing, and the present work was 
undertaken to get satisfactory data for the action of the chloroform in 
different concentrations. 
It was found that the smallest dose of chloroform tried so depressed 
the assimilatory power, that the leaf was not able to assimilate even the 
whole of its own C 0 2 of respiration. It was therefore unnecessary to 
supply air laden with C 0 2 to the illuminated leaf, and the experimental 
procedure was thereby much simplified. It sufficed merely to measure the 
1 Le5ons sur les phenomenes de la vie. Paris, 1878. 
2 Recherches sur l’action chlorophyllienne separ^e de la respiration. Ann. Sci. Nat., ser. vii, 
tome iii, 1886. 
3 Assimilatory Inhibition in Plants. Journ. Linn. Soc., 1895. 
4 W. Kegel: Ueber den Einfluss von Chlorofo m und Aether auf die Assimilation von Elodea 
canadensis. Inaug. Diss. Gottingen, 1905. 
