and the Function of Chlorophyll in Plants. 69 



constituents of the plant-cell, being consumed in oxygen, are 

 used up as the proper combustibles in the respiration of the 

 cell. This question, too, had not yet been attacked. Investi- 

 gation in intense light gives us the means of approaching it 

 more closely. 



Convincing evidence is easily obtained that all the better- 

 known formal constituents of the cell-body, even in intense 

 light, are incombustible and indestructible inside the cell. 

 This holds true of the cell-wall, of the starch-grains, also of 

 the amylaceous contents of the chlorophyll-bodies, and of the 

 fatty matters {i.e. both those enclosed in the chlorophyll-bodies 

 and the fat-globules occurring independently in the cell). There- 

 fore none of these substances in the plant is directly utilized 

 for the respiration. The cytoblast likewise, in the plant in 

 intense light, appears incombustible ; the changes which it 

 undergoes I am inclined to regard as secondary effects of the 

 alterations otherwise originated in the plasma in the light. 

 On the other hand, in the protoplasm itself it is incontrover- 

 tible that alterations take place which prove themselves to be 

 direct attacks of the oxygen-respiration taking place in light. 

 It is especially remarkable that the granules within the con- 

 tractile threads of protoplasm grow less and disappear. It 

 can with equal distinctness be demonstrated that that en- 

 velope of the cell-body which I have named the cuticular 

 layer* (Mohl's " primordial utricle ") is diminished in mass, 

 and that the granules (turned brown by iodine) which are so 

 frequently imbedded in the cuticular layer become perceptibly 

 fewer in number, so that, as it appears, hereby the most 

 essential properties of the cuticular layer are changed. 



Hence these bodies (of the chemical constitution of which 

 we possess no further knowledge) preeminently represent 

 the combustible material in the cell, which is expended in 

 respiration. Respecting their nature perhaps an explanation 

 may be given by the discovery (which I succeeded in making) 

 of a previously unknown body in the plant-cell, which, of all 

 the constituents it contains, may be designated as the most 

 sensitive and the most perishable under the influence of light. 



I ascertained, namely, that in the elementary substance of 

 the chlorophyll-bodies, likewise in the elementary substance 

 of the so-called amorphous chlorophyll in those plants which 

 as yet possess no formed chlorophyll-bodies, and in every 

 chlorophyll-green plant-cell without exception, there is present 

 and distinguishable a peculiar body, on the preparation of 



* ' Untersuchungeu iiber den Bau und die Bildung der Pflanzenzelle.' 

 Berlin, 1854. 



