FIRST VISIBLE CHANGES IN CHLOROPHYLL-CORPUSCLES. 



?>^5 



corpuscle, and which cannot be seen but can only be inferred from their consequences 

 and conditions. Confining ourselves first to the visible changes ; the old ob- 

 servations of Naegeli and myself show that in the primitively quite homogeneous 

 green substance, starch-grains, at first extremely small, become visible, usually 

 distributed in twos, threes, or more in the mass of chlorophyll of the corpuscle. These 

 enlarge and, as they meet one another during growth, become flattened and 

 applied close to one another with plane surfaces, while their free sides remain 

 rounded and become arranged more or less according to the form of the chlo- 

 rophyll-corpuscle ; occasionally, however, when they arise at the circumference they 

 protrude from the chlorophyll-corpuscle. I also observed, almost twenty years ago, 

 that, under certain circumstances, when leaves (e. g. of Tobacco and Pea) turn 



FIG. 224.— .■/ cells from an etiolated leaf of Dahlia variabilis. B the same, but older and with yellow chloroplijil- 

 corpuscles. C the yellow chlorophyll-corpuscles turned green and further developed in light. D commencement of starch- 

 formation. H advanced stages in the formation of the starch. F from the leaf of Tropaoliim majns. G and H de- 

 struction of the chlorophyll (in H yellow oil drops only remain) as the leaves turn yellow in autumn. K a cell from the leaf 

 of yicia Faba after contraction of the lining protoplasm (primordial utricle), ph the cell wall. 



yellow without being diseased, the starch-grains grow so vigorously in the chlo- 

 rophyll that the latter becomes, so to speak, entirely displaced by them, and finally, 

 in place of a chlorophyll corpuscle, there Hes a starch-grain compounded of several 

 grains (cf. Fig. 224). 



Very valuable contributions to the question with which we are here con- 

 cerned were made by A. F. W. Schimper in i88o\ I must refer to these because 

 they throw a new light on the chemical processes presumably taking place in 

 the chlorophyll. In the first place, it follows from Schimper's description that 



' Schimper, ' Unicrsuchungcn über die Entstehung der Stürkekörner: Bot. Zeit. iSSo, p. SSi. 

 — Arthur Me^er, Bot. Zeit. 18S0, Nos. 51 and 52. 



