68 M. Pringsheim on the Action of Light 



prived of colour but the motion of the protoplasm in the 

 utricle is still maintained, this will continue living for days 

 and weeks and behave quite like a normal, uninjured utricle. 

 Frequently the decolorized chlorophyll-bodies, if the expe- 

 riment has been stopped at the right time, then fall down from 

 the wall of the utricle into the level of the current, are carried 

 along and circulate with it uninterruptedly, and without being 

 altered, in the regular path of its flow, and travel the whole 

 extent of the path through the entire utricle with the same 

 velocity as the other large formed bodies contained in it (the 

 mucilaginous and ciliated corpuscles), without further dis- 

 turbing the course of the current. 



The place on which the light has fallen, however, appears 

 completely bare, and, denuded of chlorophyll-bodies, lets the 

 underlying cell-contents be directly seen. At the same time 

 the wall-coating of the green parts of the utricle may remain 

 quite unaltered and exhibit, for instance, the chlorophyll- 

 bodies, the arrangement of the chlorophyll series, the indiffe- 

 rence-streaks, &c. in normal condition quite as usual. These 

 utricles with a spot denuded of chlorophyll-bodies by light 

 present a singular appearance. 



If this utricle be placed with the same spot (now denuded 

 of chlorophyll) again exposed to intense light, in it also there 

 follows the destruction of the contents of the cell, without any 

 further decolorization of the chlorophyll bodies, just as before 

 in the green utricles which were submitted to a longer action 

 of the light, and, in fact, more quickly than in these. 



This experiment therefore proves that the destruction of the 

 contents of the green cells is independent of the chlorophyll 

 colouring-matter, and shows (since the destruction occurs or 

 does not occur in the gas-chamber under the same circum- 

 stances here also as in the green cells) that the destruction of 

 protoplasm by light is also an act of combustion evoked by 

 the heightened respiration in the light — or, in other words, 

 that with the intensity of the light the affinity of oxygen 

 for the combustible elements in the interior of the cell is in- 

 creased. But this experiment also shoios that the chlorophyll 

 as long as it lasts, acts as a protective covering, moderating the 

 injurious influence of light upon the protoplasm. 



Hence these experiments, by which is demonstrated the 

 destructively heightened respiration of plants in intense light, 

 at the same time bring to light the hitherto unimagined func- 

 tion of chlorophyll — by its strong absorption of the so-called 

 chemical rays especially, to limit the intensity of and thus to 

 regulate, the respiration. 



Now I have further taken the trouble to investigate which 



