118 RECOKD OF CURRENT RESEARCHES RELATING TO 



intensity. Blue ligbt, however, exerts a more powerful influence 

 tLian red, and tlie experiments clearly proved that the result was 

 entirely independent of the degree of diathermancy possessed by the 

 screen. 



The next point established was that the phenomena of destruction 

 of the cell and its contents in the light are altogether dependent on the 

 presence of oxygen in the surrounding atmosphere, the phenomena not 

 being presented in media free from oxygen, as in a mixtm'e of hydrogen 

 and carbonic acid ; while the removal of the fx'ee carbonic acid of the 

 atmosphere in no way interferes with the phenomena. 



The conclusion arrived at is that the destruction of chlorophyll by 

 light in the living cell is influenced and promoted by the light, and 

 that it is in no way dependent on respiration, or the decomposition of 

 carbonic acid by the plant. When the colouring matter has once been 

 destroyed by light, the chlorophyll-grains have no power to reproduce 

 it. Hence it follows that the phenomena in question cannot be a 

 normal physiological act in the life of the plant, but are a pathological 

 process. The ultimate fate of the decomposed colouring matter was not 

 accurately determined ; but Dr. Pringsheim is disposed to think that 

 it passes away in the form of various gaseous products. That the 

 injurious influences on the other contents of the cell are not the result 

 of any unknown poisonous product from the decomposition of the 

 chlorophyll-grains is proved by the fact that they occur also in cells 

 which contain no chlorophyll, as in the hairs on the filaments of 

 Tradescantia, the stinging hairs of the nettle, &c. It is possible also 

 to stop the experiment immediately after the destruction of the 

 colouring matter of the chlorophyll-grains, and to prevent its extend- 

 ing to the remaining contents of the cell. 



By these results Dr. Pringsheim was led to the important and 

 interesting conclusion that the chlorophyll, as long as it lasts, acts as 

 a protective covering, moderating the injurious influence of light on 

 the protoplasm ; and that, by its strong absorption of the so-called 

 chemical rays, it acts as a regulator of the respiration. 



The author claims to have discovered, in all green chlorophyll- 

 grains without exception, the jiresence of a hitherto unknown substance, 

 the immediate product of assimilation, from which the starch and other 

 secondary products are then formed. To this substance, which is 

 either a hydi'ocarbon, or, at all events, contains less oxygen than the 

 carbohydrates, he gives the name hypoMorin or liypochromyl. It may 

 be separated by heating the parts of the plant which contain chloro- 

 phyll for from twelve to twenty-four hours with dilute hydro^loric 

 acid, when it appears in the form of small glutinous drops, which 

 rapidly increase, and in which finally long, reddish-brown, obscurely 

 crystalline needles are formed. It is the oily ground-substance of the 

 chlorophyll-grains, soluble in alcohol, ether, oil of turpentine, and 

 benzol, but insoluble in water ; and after separation solidifies sooner 

 or later into an obscurely crystalline substance, having all the pro- 

 perties of a resin or wax. It is never absent from any chlorophyll- 

 green plant, and is more universally distributed in the chlorophyll- 

 grains than starch or oil ; but has not yet been detected in those plants 



