440 Baker . — Quantitative Experiments on 
Probably, therefore, formaldehyde may function as a stage in photo- 
synthesis ; but the production from it of sugars and other food materials 
requires light energy. This is in contradiction to most chemical theories 
on the subject ; but the results tend to confirm such a hypothesis as that 
of Collie, which postulates the production from formaldehyde of a still 
more unstable substance, keten (CH 2 =CO), before it is further elaborated 
into food materials. 
In conclusion, I have to acknowledge my obligation to Mr. T. G. Hill, 
whose advice and criticism have been of the utmost assistance throughout 
the investigation. 
EXPLANATION OF PLATES XXX AND XXXI. 
Illustrating Miss Baker’s paper on the Effect of Formaldehyde on Living Plants. 
A. Plants grown under formaldehyde in light, Expt. II. Source of formaldehyde : solid 
paraform at room temperature. Centre: Air — C0 2 + CH a O. Right hand: Air — C0 2 . Left hand : 
Air + Co 2 . 
B. Plants grown under formaldehyde in light, Expt. V. Source of formaldehyde : formalin 
at 50°. Centre: Air— C0 2 + CH 2 0. Left hand : Air — CO a . Right hand : Air + C0 2 . 
C. Plants grown under formaldehyde in darkness, Expt. VI. Source of formaldehyde : 
Formalin at room temperature. Centre: Air— C0 2 + CH a O dark. Left hand: Air + C0 2 dark. 
Right hand : Air + C0 2 light. 
D. Plants grown for fourteen days in light without C0 3 and then transferred to dark room and 
grown 14 days with formaldehyde, Expt. VII. Source of formaldehyde : Formalin at room 
temperature. Centre: Air — CO a + CH a O dark. Left hand: Air + CO a dark. Right hand: 
Air + C0 2 light. 
APPENDIX. 
In the course of the above investigation a few experiments were tried 
with other organic vapours, not aldehydes. The results obtained were all 
negative ; but, as they may serve to indicate the applicability of the method, 
they are appended here. 
The apparatus and experimental details were the same as those 
described for formaldehyde (pp. 413-18). 
Experiments on the Quantitative Effect of Carbon Disulphide 
and Acetylene on Mustard and Cress Plants in Light. 
1. Effect of Acetylene in the Air-current. 
The acetylene was produced by bubbling the air through pure water at 
known temperature, and then passing the saturated air over calcium carbide. 
A quantity of acetylene was produced equivalent to the amount of water 
vapour in saturated air at the temperature. 
