pringsheim's researches on chlorophyll. 109 



absorption in chlorophyll, is inactive; that, the visible 

 changes, vk^hether paralysis or death, iu intense light in the 

 protoplasm of the cell are seen to be the direct eHect of the 

 light; and that, in non-green cells there is an undeniable 

 light-effect. Direct proof that the colouring matter plays no 

 necessary part is afforded in the possibility of destroying green 

 cells by the insolation of a portion where there are no chlo- 

 roi)hyll-corpuscles, e.g. in a pro-embryo or branch pro- 

 embryo of Chara, where there are but few corpuscles lining 

 the wall, or the part of a living Nitella-coW. bared of chloro- 

 phyll corpuscles, as described on page 92. In such cases de- 

 struction proceeds as rapidly as it would if chlorophyll were 

 present. Again, those species of S/nrogyra are the most 

 sensitive which have feebly coloured chlorophyll-bands, and 

 the most widely separated bands. Cells with approximated 

 and deej)ly coloured bands are not more strongly affected by 

 light, as would be the case were the destruction of cell 

 contents a consequence of that of the chlorophyll colouring 

 matter; on the contrary, there is greater immunity from 

 light effect. Differences in this respect are often very 

 marked in one and the same species of Spirogyra. The 

 effect of dissemination and aggregation of chlorophyll in re- 

 tarding the action of light on the shaded part is easily 

 observed in all green cells. The colouring matter is less sen- 

 sitive to light than the other sensitive elements of the cell; 

 and this is the case, as experiments in red light show, not 

 only for lights of different intensities, but also of different 

 spectral breadths. 



The destruction, then, of protoplasm and the death of cells 

 in light is a true light effect, independent of the destruction 

 of ctilorophyll colouring matter, taking place in green cells, 

 as well as in those otherwise colorred, before complete de- 

 struction of the colouring matter, ind it is not brought about 

 through light-absorption in the chlorophyll-corpuscles. It is 

 developed by absorption in the protoplasm itself of all the 

 illuminating rays of the spectrum, the red rays up to those 

 of wave lenjiths of "00061 mm. being excluded from the 

 action, and the chlorophyll colouring matter, instead of 

 increasing the light-effect upon the cell contents of the part 

 it shades, lessens the same. This, the evident, and, indeed, 

 necessary effect of the colouring matter, has been hitherto 

 entirely overlooked in estimating its physiological importance 

 in respiration. 



As death of the cell is not always accompanied by such 

 striking changes as displacement of the nucleus, cessation of 

 movement, &c., which are seen in Spirogyra, Nitella, and 



