422 Baker . — Quantitative Experiments on 
Experiment VII. November, 1912. 
Light without carbon dioxide, and then darkness. 
Source of formaldehyde : formalin at room temperature. 
Temperature range, 6 ° to 15°. 
Duration , 28 days. 
Atmosphere. Orig. dry weight. Final dry weight . Final/ or ig. weight. 
Air — C 0 2 + CH 2 0 , dark 0*3845 grm. 0*2869 g rm * 74*62 % 
Air + C 0 2 , dark 0*3845 „ 0*3175 „ 82*52% 
Air + C 0 2 , light 0*3830 „ 0*3645 „ 95*!7 % 
Air - C 0 2 , light 0*3840 „ 0*1936 „ 50*42 % 
Notes. — A photograph of these cultures is shown in PI. XXXI D. The 
effect of formaldehyde was immediately toxic. The first symptom was a 
collapse of the hypocotyls just below the cotyledons, and after that no 
etiolation was produced. The relative large weight of both the c dark 5 
cultures, compared with the ‘ light * culture without carbon dioxide, was 
no doubt due to decreased respiration under the conditions obtaining 
in the dark room, where the temperature was uniformly lower than in the 
conservatory. 
Discussion of Results. 
The cultures in light, with traces of formaldehyde in the air, show 
uniformly an increase in dry weight compared with the cultures free 
from all carbon. This increase in dry weight seems to depend also, 
to some extent, on the amount of formaldehyde present in the air, but 
does not appear to be proportional to it. That is, after a certain percentage 
of the vapour in the atmosphere, a greater concentration does not cause 
a corresponding increase in dry weight. This seems to indicate that the 
maximum increase in weight possible with formaldehyde has been attained ; 
and that, therefore, the percentage of the gas was no longer a determining 
factor in the reaction. The increase in dry weight is not so great as 
the decrease due to respiration, so that plants will not continue to grow 
indefinitely in formaldehyde. The increase due to formaldehyde is not 
so great as that due to carbon dioxide, even when the proportion of 
potential carbon in the air is greater in the former vapour. It would be 
natural to attribute the apparent gain in weight, under the influence of 
formaldehyde, to a decrease in the respiratory activities of the plants, but 
for the fact that the dark cultures show increased respiration due to form- 
aldehyde stimulation. 
Benedicenti and De Ton 1 have performed a series of experiments on 
Nicotiana ) Pap aver , and Pelargonium , and find that these plants show uni- 
formly an increase in respiration, under the stimulus of formaldehyde vapour 
in darkness, until poisonous concentrations are reached. The only possible 
inference is, therefore, that the plant can make use of formaldehyde, for 
1 Benedicenti and De Ton: Atti del Reale Istituto Veneto di Scienze, Lettere ed Arti, 1901- 
1902, t. Ixi, p. 329. 
