1903.] Assimilation of Carbon Monoxide ~by Green Plants. 131 



were reached, oxygen was added so as to keep the amount of this gas 

 approximately equal to that in normal air. 



One very significant fact was noticed during the experiments. 

 When in bright sunshine a negative pressure was always observed in 

 the bell jars containing plants growing in carbon monoxide. This 

 result tends to confirm Baeyer's theory of photosynthesis. In normal 

 photosynthesis the volume of oxygen given off is equal to the volume 

 of carbon dioxide undergoing decomposition. If, however, carbon 

 monoxide be used directly by the plant, only half the amount of 

 oxygen would be given off, hence the negative pressure. 



Experiments were also made to find if starch was formed in plants 

 growing in carbon monoxide. Tropceolum plants growing in water 

 culture solution were placed in the dark for 48 hours, when the leaves 

 were shown by the iodine test to be free from starch. Some of the 

 V plants were then placed in air free from carbon dioxide ; others in 

 carbon dioxide free air, but containing 10 per cent, of carbon 

 monoxide. All were then exposed to sunlight for three days, and 

 again examined for starch. The plants grown in carbon dioxide free 

 air had formed no starch, whilst those grown in carbon monoxide 

 gave the iodine test most markedly. Sections of the green stems 

 showed quantities of starch grains in the ground tissue, especially 

 crowded around the vascular bundles, in the plants grown in carbon 

 monoxide, but none in those grown in carbon free air. 



Experiments on the germination and growth of seeds in carbon 

 monoxide also gave satisfactory results. Seeds of Lepidium sativum 

 were planted in sterilised sand and placed in a mixture of 65 per cent, 

 carbon monoxide and 35 per cent, oxygen. The seeds germinated 

 and formed healthy plants, growing quite normally for three weeks. 

 Certain preliminary determinations of the amount of carbon in the 

 seeds and in the plants point to the accumulation of organic carbon, 

 and as the only possible source for this increase of carbon is the 

 carbon monoxide, some of it must have been assimilated. These 

 results are so important and the results so striking that it has been 

 thought advisable to repeat the determinations with new and specially 

 devised apparatus before quoting figures. Also it is intended to carry 

 out further experiments with carbon monoxide, and with compounds 

 in which the CO-group exists in combination. 



In all these experiments with carbon monoxide, great care was 

 taken that efficient absorbers of carbon dioxide were used, and the 

 pressure in the bell jars was regulated by potash-sealed valves. 



The present communication is only a note to indicate the general 

 bearings of the research, and does not give any account of many 

 experiments and observations of interest which the authors hope to 

 give^ later in a detailed paper. 



VOL. LXXII. L 



