THE VEGETABLE CELL. 



13 



Cells of the albumen of Sagu<i fcedigera. 



Fig. 16. 



that tlie membrane of tlie young cell and likewise the inmost layers of 

 full grown cells are composed of cellulose^ the intermediate and outermost 

 layerS; on the con- p, -^ 



trary, of other com- 

 pounds, which are 

 subsequently form- 

 ed and deposited on 

 the outside of the cel- 

 lulose membrane. 

 Against this I have 

 shewn (^^Botanisclie 

 2^eitunf 184:7,4:97) 

 that the chemical 

 researches by which 

 their deductions are 

 supported; were im- 

 perfect ; that the 

 outermost layers of cell-membrane are composed in like manner of cellu- 

 lose, but are infiltrated with foreign compounds, which prevent the re- 

 action of iodine and sulphuric acid ; that the date of origin of a layer 

 must not be deduced from the che- 

 mical reaction, since both the inner 

 and outer layers may undergo a che- 

 mical metamorphosis, which does not 

 stand in any connexion with the time 

 of its origin j and that therefore ana- 

 tomical groxmds alone can serve for 

 the decision of the order in which dif- 

 ferent layers have been developed. — 

 Lastly, in reference to the statement 

 that the thick walled cells of the 

 albumen of PhytelepJias^ Iris, &c. 

 (figs. 14, 15), and the so-called col- 

 lenchyma cells {^g. 16) possess uni- 

 form, and not lamellated, walls, and 

 that consequently their primary mem- 

 brane itself has increased in thickness; 

 this assertion depends simply upon im- 

 perfect investigation. If the authors had treated these cells with sulphuric 

 acid of the proper degree of concentration, they would have found the 

 lameUation. — In short, the researches which I was caused to undertake 

 by the objections of Harting and Mulder, served only to strengthen the 

 grounds on which I had built my theory of the growth of cell-membranes. 



The secondary ceU-membranes deserve a separate mention. Taken 

 altogether, it is seldom that they appear to the eye, as the primary 

 membrane does, in the form of an uniform smooth pellicle, as it 

 vere a hardened mncilage, for example in the Gonfervm and in 

 many hairs. Whether in such a case they are really devoid of 

 special structure, is doubtful, for such cells, when drawn out 

 lengthways, sometimes tear in an oblique direction, so that they 



Cells from tlie leafstaJlc of Nymphma alba* 



