ADDENDA TO BOOKS I. AND II. 573 



Zeitung, p. 521, et seq.). The young cells consist of a nucleus, surrounded 

 by several concentric layers ; both these and the nucleus are coloured 

 blue by iodine. A coagulated gelatinous layer encloses the whole in the 

 form of a cell. These cells soon disappear as amylum-cells, since they 

 are gradually converted into a substance which becomes brown with 

 iodine (! ! !), and so forth. 



1847. Karl Muller, Contributions to the History of Development of 

 the Vegetable Embryo (in the Botanische Zeitung, p. 760.). The first 

 cell of the embryo undoubtedly proceeds from the cytoblastema ; the 

 most indubitable confirmation of Schleiden's theory of cells (?).* 



ffofmeister, Researches into the Process of Fertilisation in the (Eno~ 

 thereat (in the Botanische Zeitung, p. 788.). The first cell in the embry- 

 onal vesicle is formed by a sudden production of a septum ; consequently 

 the most indubitable refutation of Schleiden's theory of cells (?). 



Page 48., add to History and Criticism. 



The whole of Hartig's view has, moreover, been refuted by Hugo von 

 Mohlf , in his usual profound manner, and it can scarcely be a matter for 

 scientific discussion again. Harting \ makes far more solid objections to 

 Mohl's view of the gradual development of the cell-wall, and with him, 

 in part, Mulder , both in an anatomical and chemical point of view. 

 Hugo von Mohl | refutes the opinions of both, and also answers the sub- 

 sequent defence of Harting \. in a special treatise.^ Harting stated that 

 the original, yet unthickened, cell-membrane is perforated, and exhibits 

 in its earlier conditions, when treated with iodine and sulphuric acid, a 

 great number of white transparent pores, which subsequently become 

 closed by the layer of deposit upon the outer surface of the cell-walls. 

 On the other hand, Mohl repeats that these pores, previously seen and 

 described by me**, are not perforations, but closed by a delicate mem- 

 brane, the original membrane of the cell, which membrane also assumes 

 a blue colour, though very light. Mohl does not mention what I have 

 met with frequently in delicate transverse sections ; for instance, in the 

 parenchyma of the cabbage stalk, in the albuminous body of the Tagua 

 nut (vegetable ivory), &c., that a fine streak extends between the cells, 

 of a substance which remains almost colourless, while the cell-mem- 

 brane becomes deep blue with iodine and sulphuric acid. When the 

 section was successful, I always saw this substance separated into two 

 portions (the original membranes of the two contiguous cells) by a 

 delicate line. Harting further deduces, from micrometric measure- 

 ments, that the cavity of the cell does not become smaller through 



* This author, as his researches in Monotropa show, cannot even distinguish the 

 embryo from the endosperm. 



f H. v. Mohl, Observations on the Structure of the Vegetable Cell. Botanische 

 Zeitung, 1844, p. 273. 



\ Harting, Microscopic Researches into the Walls of vegetable Cells (in Scheikondige 

 Onderzoekingen ; extract by H. v. Mohl in the Botanische Zeitung, 1846, p. 64.). 



Mulder, Physiological Chemistry, translated by Moleschott ; in English, by 

 From berg. 



|| H. v. Mohl, On the Growth of Cell-membrane. Bot. Zeit. 1846, p. 337. 



| Harting, Letter to H. v. Mohl, &c. Bot. Zeit. 1847, p. 337. 



^ H. v. Mohl, Investigation of the Question, Is Cellulose the Element of all Vege- 

 table Membranes? Bot. Zeit. 1847, p. 497. 



* Wiegmann's Archiv, 1838, vol. i. p. 49. ; Beitr. z. Botanik, vol. i. p. 16. 



