the Effect of Formaldehyde on Living Plants. 441 
Amount of Acetylene in the Air. 
Temperature of water varied from i° to 9 0 . 
Partial pressure of water — from 4-9 mm. to 8-6 mm. = p. press. C 2 H 2 . 
From this it can at once be calculated by simple proportion that at 
ordinary atmospheric pressure of 760 mm. the partial pressure of acetylene 
is 0-64 % to 1-13 % of the total atmospheric pressure. 
Results. — Effect of C 2 H 2 in Light. 
Plant used : Cress ( Lepidium sativum). 
Several unsuccessful experiments were devoted to working out the 
general method, from March to June, 1910. 
Final Experiment, June, 1910: 
Atmosphere. Orig. dry weight. Final dry weight. 
Air — C 0 2 + C.jH 3 0*2015 grm. 0*1002 grm. 
Air — C 0 2 o*20io „ 0*1387 „ 
Air + C 0 2 o 1996 „ 0*2520 „ 
Final /orig. weight. 
497 % 
6o*o% 
i58-o% 
Notes on the Morphology of the Cultures. 
The effect of acetylene on the plants was to render them rather stout in 
appearance, about half their normal height, and non-heliotropic. 
Conclusions. — Even from this one result it is immediately obvious that 
there is no assimilation of acetylene. The loss in weight, in excess of the 
culture without carbon dioxide, is interesting as indicating that the gas 
stimulated the respiratory activities of the plants. 
2. Effect of Carbon Disulphide in the Air-current. 
Amount of Carbon Disulphide introduced into the Air. 
Determined in a separate experiment by weighing the diffusion bulb 
before and after the passage of a known volume of dry air. 
V allies : 
Dimensions of 
Capillary. 
Length. Bore. 
Vol. 
Properties of Air. 
Press. 
Temp. 
Time t 
in hours. 
Weight given off 
in t hours. in i hour. 
litres. 
mm. 
grm. 
grm. 
4 cm. 
0*5 mm. 
28*31 
760 
I4 ° 
6*o 
0*0045 
0*00075 
4 cm. 
0*5 mm. 
14*26 
767 
13 ° 
2*5 
0*0029 
0*00125 
10 cm. 
0*5 mm. 
3*54 
not obs. 
1 6° 
1*125 
0*0002 
o*ooo 1 8 
As 1 litre of air weighs about 1*32 grm., the mean per cent, by weight 
of carbon disulphide in the air is about : 
With 4 cm. capillary . . 0-00135 
„ 10 cm. „ . . 0*00042. 
