THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY. 



[THIRD SERIES.] 

 No. 22. OCTOBER 1859. 



XXV. — On the supposed Existence of Cellulose in Starch-grains. 

 By H. von Mohl *. 



On no vegetable structure has so great a number of micro- 

 chemical researches been instituted as upon starch-grains ; and 

 of none have the structure and chemical composition, in the 

 course of time, been so contradictorily explained. The view of 

 Raspail, that the starch-grain consisted of a vesicular envelope 

 insoluble in water, with soluble gummy contents, was overturned 

 by the researches of Fritzsche and of Payen, who appeared to 

 have demonstrated beyond all doubt that the starch-grain con- 

 sisted of superimposed layers, formed of one and the same che- 

 mical compound throughout the whole thickness of the grain ; 

 but Nageli believed, in his earlier researches at least, that he 

 could discern an outer cellulose membrane, — which opinion was 

 again questioned by myself. Muschke (Journ. f. Prakt. Chemie, 

 lvi. p. 400) still more strongly asserted the presence of cellulose 

 in the starch-grain, thinking he had found the latter to consist 

 of a number of concentric membranes formed of cellulose, be- 

 tween which the starch-substance was deposited, and this in a 

 double modification — one soluble in water, which formed the 

 bright layers of the starch-grain, and one insoluble, of which 

 the dark layers were composed. All these accounts, however, 

 may now be regarded as out of date, since the recent researches 

 of Nageli ('Die Starkekorner/ Monographic, 1858) prove 

 indubitably that the whole starch-granule, in all its parts, is 

 composed of two distinct chemical compounds, which in his 

 view form a kind of diffusion f. He arrived at this conclusion 



* Bot. Zeitung, July 1st & 8th, 1859; translated by A. Henfrey, F.R.S. 



t A very long account of the structure and development of starch has 

 just been published by Trecul in the * Ann. des Sc. nat.' ser. 4. t. x. It does 

 not contain any new matter of great importance : he advocates the view 



Ann. fy Mag. N. Hist. Ser. 3. Vol.'xw. 16 



