STARCH-FORMING CORPUSCLES. 317 



(Schimper here somewhat inaccurately terms them Leucophyll) are all only very 

 feebly coloured yellow, or are not coloured at all. In the cases investigated they, 

 like the i bloroi hyll-corpuscles which the same cells would have contained under 

 normal circumstances, produced the starch -grains at their peripheral portions. 

 Not less important, with respect to the difference between starch-forming corpuscles 

 and chlorophyll-corpuscles, is Schimper's further statement, that in the case of a plant 

 {Tradescanh'a rubella) from the assimilating chlorophyll of which the large starch- 

 grains had been allowed to disappear entirely in the dark, and which was now 

 placed in a feeble light, no starch was produced in the normal chlorophyll-corpuscles 

 of the leaves here developed ; but, on the other hand, abundance of starch arose 

 in the starch-forming corpuscles — i. e. in the pseudo-chlorophyll-corpuscles of the 

 vascular bundle-sheaths of the leaves and stem. Schimper draws from these facts 

 the following conclusion. The fact that the development of starch in the meso- 

 phyll of the leaf depends on the same conditions as assimilation, while in other 

 parts of the plant it occurs independently of light, so long as reserve-materials 

 are present, can only be explained by assuming that in the first case it is exclusively 

 a product of the assimilation of the chlorophyll-corpuscle in which it appears, while 

 in the second case it must have in part (I think entirely) a different origin.' 



Finally, Schimper expresses himself as follows with respect to the invisible, 

 purely chemical processes : — ' It is clear that the starch which appears as the 

 first evident product of assimilation (in the true chlorophyll-corpuscles) does not 

 originate directly from carbon dioxide and water, but that more or less numerous 

 intermediate products, still unknown or at any rate known with less certainty, 

 are interposed. We may assume that the substances conveyed to the chlorophyll- 

 corpuscles are identical with one of these intermediate products, or are at 

 any rate very similar to them ; and hence the transformation to starch of the 

 assimilated matters formed there and then, and of those conveyed from other 

 organs, is effected by one and the same process' (probably similar processes 

 is meant). 



I cannot here avoid repeating my view on the formation of starch in the 

 assimilating chlorophyll, already expressed in the '■ Experimenial-physiologie' (1865); 

 and so much the less, because it has been in the meantime grossly misrepresented, 

 and falsely quoted, by writers unacquainted with vegetable physiology. I there 

 said (p. 327), 'If, after all, I regard the starch in the chlorophyll as one of the 

 first products of assimilation, it is not therefore to be said that carbon dioxide and 

 water unite forthwith to form molecules of starch within the chlorophyll-substance, 

 oxygen being evolved. It is not even necessary that any carbo-hydrate whatever 

 should arise immediately ; it is possible, and probable, that the process accompanied 

 by the evolution of oxygen is a very complicated one, from which the formation 

 of starch results only by numerous chemical metamorphoses. It is, indeed, not 

 impossible that certain more immediate constituents of the green plasma itself take 

 part in the process — that decompositions and substitutions, for example, take place 

 in the molecules of the green protoplasm. This possibility obtains some probability 

 from the observation that in many (not all) cases the chlorophyll-substance gradually 

 decreases in quantity and at length disappears entirely, while the starch-grains are 

 growing in it,' etc. With reference to Schimper's results, I am now strongly inclined 



