BOTANICAL GAZETTE. 4j 



duced, although the amount of heat that passes is very small. It is 

 thus seen that the phenomena in question are not the result of heat. 



The next point determined by Dr. Pringsheim is that the effects are 

 not produced in an atmosphere devoid of oxygen. This was the case 

 whether the oxygen was replaced by pure hydrogen or by a mixture of 

 hydrogen and carbon dioxide; while the removal of the carbon diox- 

 ide from atmospheric air was altogether without effect on th*^ phenom- 

 ena. The conclusion drawn is that the decomposition of chlorophyll 

 in the living plants is a process of combustion which is influenced and 

 promoted by the action of light, and which is not related to the de- 

 composition of carbon <lioxide by the plant. When the green color of 

 the chlorophyll-grains has been partially destroyed, it cannot be 

 restored, even though the cell continues to live; from which it is in- 

 ferred that the result is not a normal physiological, but a ])athological 

 effect. No substance was found in the cells which might be regarded 

 as the product of the decomposition of the chlorophyll, nor was any 

 oil or starch detected in the etiolated cell, nor any formation of grape 

 sugar or dextrine. The assumption is therefore that the products of 

 decomposition are given off in the gaseous form. 



The conclusion is drawn that the decomposition produced in the 

 protoplasm, and in the other colorless cell contents, is the direct effect 

 ot the photochemical action of light. That it is not due to the injuri- 

 ous influence of the products of decomposition of the coloring matter 

 of the chlorophyll is shown by the fact that it takes place equally in 

 cells destitute of chlorophyll, such as the hairs on the filaments of 

 Tradcscantia, the stinging hairs of the nettle, &c. It is, on the other 

 hand, dependent on the presence of the oxygen, or is a phenomenon 

 of combustion. 



The results of a variety of experiments leads Dr. Pringsheim to the 

 important and interesting conclusion that the chlorophyll acts as a pro- 

 tective substance to the protoplasm against the injurious influence of 

 light, diminishing the amount of combustion, or, in other words, act- 

 ing as a regulator of respiration. 



He then proceeds to investigate what are the substances which be- 

 come oxidized in the process of respiration. In every cell, without 

 exception, that contains chlorophyll, Pringsheim finds a substance that 

 can be extracted by immersion in dilute ' hydrochloric acid for from 

 twelve to twenty-four hours, to which he gives the name JixpocJilorin or 

 hypochromyl, and which he believes to be the primary product of the 

 assimilation of the chlorophyll. It occurs in the form of minute vis- 

 cid drops or masses of a semi-fluid consistency, which gradually 

 change into long red-brown imperfectly crystalline needles. It is sol- 

 uble in alcohol, ether, turpentine and benzol, but insoluble in water 

 and in a solution of sodium chloride. It becomes gradually oxidized 

 on exposure to an imperfectly crystalline resinous substance. It is 

 probably an ethereal oil, and an invariable accompaniment of the col- 

 oring substance of chlorophyll, and even more universally distributed 

 than starch or oil. It has not yet been detected in those plants which 



