Development f and Structure of the Vegetable Cell. 187 



ture agreeing with the contour of the epidermic cells, such as 

 indeed is possessed by the outermost coat of the epidermis be- 

 longing to the epidermic layers, characterized by Mohl as 

 " cuticular layers." 



If, however, the homogeneous cuticle, which, when old, may 

 be slightly granular or striated, but which exhibits no cellular 

 structure, is to be regarded as derived from the first excretion- 

 layer of the first cell, we must ascribe to this first excretion- 

 layer the property of appropriating material out of its vicinity ; 

 and as it cannot anywhere find materials ready prepared so as 

 to add them to its substance by apposition in the fashion of in- 

 organic growth, we shall further have to attribute to it the pro- 

 perty of preparing the necessary materials for itself from hetero- 

 geneous matters by virtue of the chemical affinity inherent in 

 its own substance. 



To this first excretion-layer of the first cell we must thus 

 ascribe the faculties which ought essentially to belong only to 

 the interior cell, to which it is indebted for its existence. It 

 must possess in itself the properties of the assimilating mem- 

 brane ; it must be, not a mechanically excreted educt of the 

 exuded cell-juice, but a portion of an organized structure, the 

 membrane of an independent cell, within which the enclosed 

 cells have been produced. 



With this view the results of the investigation of the develop* 

 mental history of this structure published by me in 1848 (Bot. 

 Zeitung) perfectly agree. 



I ascertained then, and can repeat the experiment with faci- 

 lity at any time, that by means of endosmotic fluids (such as 

 dilute mineral acids, solution of sugar, &c.) a delicate structure- 

 less niembraue may be detached from the young embryo in its 

 different stages of development in the embryo-sac : the youngest 

 state of this membrane is consequently the membrane of the 

 germinal cell ; and it may be demonstrated by the same means 

 to be the outermost coat of all still cambial organs of the plant 

 in course of development. 



The objection that a cell cannot so far enlarge itself as to 

 overspread an entire plant, originating from the idea of the 

 growth of the cell-membrane by accretion, is consequently not 

 applicable; for the cell-membrane, and more particularly the 

 cuticle, as already said, cannot increase itself by accretion, the 

 material of which it is composed not being found in solution in 

 its vicinity. 



An independent growth of the cuticle, in many cases quite 

 unconnected with the adjoining cell-wall, may be recognized 

 with certainty in the examples referred to at page 423, vol. xiii. 

 and represented in Plate VI. figure 45. 



