the Effect of Formaldehyde on Living Plants . 42 t 
percentage of formaldehyde in the air was about four times as great as 
in Experiments III and IV. 
Experiment V. November, 1912. 
Source of formaldehyde : formalin at about 50°. 
Temperature range, 5 0 to 15 0 . 
Duration , 28 days . 
Atmosphere. 
Air - C 0 2 + CH 2 0 
Air — C 0 2 
Air + C 0 2 
Orig. dry weight. 
0*3780 grm. 
0*3840 „ 
0-3830 >» 
Final dry weight. 
0*3715 grm. 
0*1936 Ti 
0-3645 „ 
Finat, / orig. weight. 
98-28 % (?) 
5o-4 2 % 
95-17 % 
Notes . — A photograph of these cultures is shown in PI. XXX B. 
Formaldehyde at this concentration had decidedly toxic effects. The chief 
symptoms were stunted growth, little heliotropism, and a collapse of the 
hypocotyls. This last effect caused some of the plants to fall over into 
the potash solution, and, in spite of washing, some of this was probably 
retained over the surface, which caused the great increase in dry weight. 
This has, therefore, no special significance. 
B. EFFECT OF FORMALDEHYDE IN THE DARK. 
The general methods were the same as before, only the whole apparatus 
was set up in a dark room and the bell-jars covered with black paper ; also 
the check dark experiment had carbon dioxide in the air. 
Experiment VI. November, 1911. 
Source of formaldehyde : formalin at room temperature. 
Temperature range, 8-5° to 13*3°. 
Duration , 33 days. 
Atmosphere. Orig. dry weight. 
Air — C 0 2 + CH a O, dark 0*3895 grm. 
Air + C 0 2 , dark 0*3960 „ 
Air + C 0 2 , light 0*3840 „ 
Final dry weight. 
0*1498 grm. 
0*2247 „ 
0 - 31.55 » 
Final /orig. tv eight. 
38-48 % 
56-50 % 
79-56 % 
Notes . — A photograph of these cultures is shown in PL XXXI C. The 
effect of formaldehyde in the dark was not notably toxic. The diminished 
etiolation and slight development of root-hairs were the most noticeable 
features of the formaldehyde culture, and these effects were in part produced 
by deficient water-supply. 
A second experiment was performed to see whether a gain in weight 
would be shown in the dark if chlorophyll had been formed in the leaves 
first. The two ‘ dark ’ cultures were first kept fourteen days in light, without 
carbon dioxide, and then the bowls were transferred bodily into the dark 
room. The formaldehyde bell-jar was not lifted at all in the process. 
G g 2 
