1906.] Mechanism of Carbon Assimilation in Green Plants. 321 



exhausted and refilled six times. A similar tube without any catalase was 

 treated in the same way. When the tubes had been filled with oxygen-free 

 carbon dioxide for the sixth time, they were sealed off at the capillary 

 portion and exposed to sunlight. In the course of an hour the gelatine in 

 the tube containing the enzyme was swollen with bubbles of gas, and the 

 chlorophyll film became distorted and broken up. The only visible change in 

 the other tube was the bleaching of the chlorophyll. When the tubes had 

 been exposed to light for two days they were attached to a Ttipler pump by a 

 short piece of rubber pressure tubing. After completely exhausting the 

 system on the pump side of the capillary, the latter was broken off inside the 

 pressure tubing, and the gas pumped out through a tube packed tightly with 

 soda-lime, which absorbed all but a trace of the carbon dioxide. The tube 

 containing the catalase yielded - 6 c.c. of oxygen, with a trace of nitrogen, 

 while the other gave a minute bubble of nitrogen only, the latter being 

 derived in each case from the air present in the carbon dioxide before its 

 passage over the red-hot copper. Two more similar experiments gave 2 c.c. 

 and T2 c.c. of oxygen respectively. 



It was found that if the exposure to light was continued until the chloro- 

 phyll was bleached, the enzyme was poisoned by the accumulating formal- 

 dehyde. This is precisely what occurs in the plant under similar conditions ; 

 that is, when the protoplasm only has been killed. 



According to the analysis of the photosynthetic process given in the paper 

 already referred to, where it was shown that the condensation of formal- 

 dehyde to carbohydrates is dependent upon the healthy condition of the 

 protoplasm, one would expect non-chlorophyllous living cells to be able to 

 bring about this change. It appears from the feeding experiments of 

 Bokorny, Bouilhac, and Treboux that light is necessary in the case of green 

 plants, and we have found that this is also the case with the white petals of 

 Saxifraga Wallacei, which are capable of forming starch in the light from a 

 - 001-per-cent. solution of formaldehyde, though no condensation takes place 

 in the dark. In a further series of experiments these petals, when quite free 

 from starch, were painted with chlorophyll solution, and floated on water 

 charged with carbon dioxide in a bottle placed in the light. In the course of 

 a day they were found to contain starch. In this case we have what is 

 essentially a green leaf arranged in a different way, though it is, of course, a 

 very inefficient substitute for the natural organ. 



As it was of interest to ascertain whether formic acid is actually produced 

 as an intermediate product in the photolytic reduction of carbonic acid to 

 formaldehyde, an experiment similar to those described in Series I above 

 was performed, the gelatine being dissolved in a solution of sodium bicar- 



