120 VEGETABLE CELLS. 



cells have been merely the contents of secondary cells 

 contracted through external influences. Two reasons 

 especially strengthen this opinion in my mind. In one 

 case Schleiden figures three secondary cells in one parent- 

 cell. Now, as I shall hereafter show, it is an universal 

 law that in the formation of the cells of tissues only two 

 secondary cells are formed in each parent-cell. If, then, 

 one wall have been overlooked in consequence of the 

 alteration of the contents, so readily may the other. 

 Schleiden further says that he has often seen two cells 

 inside one cell,* especially after the application of nitric 

 acid. This is in contradiction with the observation he 

 made, that the young cell-membranes are wholly dissolved 

 in distilled water, in a very short time.f If this will 

 happen in water, it will certainly happen much more 

 quickly in nitric acid. It is in the highest degree pro- 

 bable from this, that Schleiden saw merely the contracted 

 contents, not the young cell and its membrane; and, 

 moreover, in that condition in which the action of the 

 acid has already made the delicate membrane of the 

 secondary cells indistinct, while the older and firmer 

 membrane of the parent-cell still remains visible. 



Since then a better appreciation of the membrane, and 

 the recognition of the mucilaginous layer, rendered all 

 earlier observations uncertain, I instituted a new series 

 of investigations. If the tissue of the higher plants were 

 really produced by free cell-formation, this could only be 

 proved by seeing the young free cells, free in uninjured 

 and unaltered parent-cells. I must confess that I never 

 have arrived at this. In most cases this is, indeed, no 

 proof at all of the contrary ; since admitting a free cell- 

 formation, it would, in my opinion, be unlikely, in the 

 majority of cases, that the delicate membranes should be 

 seen in the but slightly transparent mucilage, previously 

 to their union to form a wall. On the other hand, I be- 

 lieve that in certain other instances it might possibly have 



* Grundz. 2d Ed. p. 202. f Miiller's Archiv., 1838, p. 145. 



