II. VON MOHL ON CELLULOSE. 95 



ARTICLE IV. 



Investigation of the question: Does Cellulose form the basis of all 

 Vegetable Membranes? By HUGO VON MOHL. 



[From the Botanische Zeitung, vol. v. p. 497 et seq."] 



IN a former paper* I laid down the anatomical and chemical 

 reasons which led me to persist in maintaining the doctrine of 

 the growth of the membrane of the elementary organs of plants 

 propounded by myself and attacked by various writers, and 

 induced me to reject the view, defended by the Utrecht professors, 

 Mulder and Harting, that the outermost layers of those mem- 

 branes are the youngest and the inmost the oldest. Since that 

 paper was written I have carried through a long series of new 

 observations for the further elucidation of the conditions here in 

 question, the results of which, so far as relates to the chemical f 

 characters of vegetable membranes, 1 believe may be published 

 with advantage, because they may serve to throw light upon 

 some points as yet unknown, and to refute the chemical evidence 

 brought forward by Harting and Mulder in favour of their view. 

 In the Essay already referred to, I closely discussed the 

 opposition presented by the deductions drawn by Mulder and 

 Harting on one side, and by myself on the other, from the known 

 reaction of cell-membranes when acted on by sulphuric acid and 

 iodine. My opponents are of opinion that the circumstance of 

 thin recently formed membrane being coloured blue by iodine 

 and sulphuric acid, while in many full-grown cells only the inner 

 layer manifests this reaction, while the outer are tinged yellow 

 by these two substances, gives ground for the deduction that 

 these outer layers have been formed subsequently to the others, 

 and that the inmost layers of the full-grown cells are the same 

 membranes which constituted alone the wall of the young cell. 

 On the other hand, I asserted that this conclusion is too hasty, 



* Bofanische Zeitung, vol. iv. p. 337 et scq. Translated in the Annals of 

 Natural History, vol. xviii. p. 145 et seq. 



t I shall speak of the anatomical conditions on another occasion. 



