the Effect of Formaldehyde on Living Plants. 419 
air, and subtracting from this loss in weight the weight of water and alcohol 
caught in a calcium chloride tube. 
It was not thought worth while to make a long series of observations, 
through a range of temperatures and pressures in order to ascertain the 
exact percentage of vapour in the air at any time during the experiment 
(as, of course, both temperature and pressure varied widely during the 
course of a single day) ; but these values indicate roughly the concentration 
of the vapour under mean conditions. They are probably somewhat higher 
than the actual concentration in the bell-jar, because the caustic potash 
solution will dissolve and also destroy a certain fraction of the formaldehyde 
bubbled through it. 
Values : 
Source of CHf). 
Properties of the air. 
Weight C/fO 
% C/fO in air 
Vol. 
Press. 
Temp. 
in vol. V. 
by weight. 
litres. 
mm. 
grm. 
Diffusion bulb, cap. 4 cm., 
0-5 mm. bore . . . 
25-3 
762 
*3° 
0-0002 
0-0006 
Formalin solut. about 40 % 
28-316 
not obs. 
1 6° 
0-1782 
0*5303 
56-632 
)) 
1 6° 
0-3464 
o* 5 i 55 
Paraform in tube . . . 
28-316 
757 
1 6° 
0-0301 
0-0872 
28-316 
758 
i7° 
0-0304 
0-0880 
For comparison, 
it may 
be noted 
that the 
maximum 
percentage of 
carbon dioxide normally present in the atmosphere is only 0-04 %, so that 
there is an adequate supply of potential carbon for purposes of photo- 
synthesis produced by both the last two methods of producing formaldehyde. 
A. EFFECT OF FORMALDEHYDE IN LIGHT. 
The plants used in all these experiments were White Mustard — Brassica 
alba , Boiss. — and about sixty seeds were the starting-point for each culture. 
Experiment I. May, 1911. 
Source of formaldehyde : formalin in a diffusion bulb. 
Amount of formaldehyde in air, about 00006 per cent. 
Temperature range, n° to 23°. 
Duration , 23 days. 
Atmosphere. 0 rig. dry weight. Final dry weight. 
Air — C0 3 + CH 2 0 0-4050 grm. 0-2265 grm. 
Air - C0 2 0-4015 „ 0-2175 » 
Air + C0 2 °'3995 >> 0-4255 >> 
Final / orig. weight. 
55*9% 
54*2 % 
% 
106-2 
Notes . — The slight increase in weight of the formaldehyde culture 
made it appear possible that, with a greater concentration, assimilation 
might take place. 
