124 VEGETABLE CELLS. 



to Mohl, this is of very general occurrence. From my 

 own researches, I believe that I may venture to affirm, 

 that, with the exception of those young cells, in which the 

 cavity is filled with homogeneous mucilage, the muci- 

 laginous layer is always present in cells so long as they 

 retain their vitality. It is well known that the thickening 

 of the cell- walls is effected by a deposition of new layers. 

 These new layers are produced between the cell-wall and 

 the mucilaginous layer. This fact admits of no other 

 explanation than this : that the mucilaginous layer (or the 

 contents through this layer) secretes organic, unazotized 

 molecules which form the new thickening layer. 



I have further shown, in the first part of this essay, that 

 in consequence of disturbing external influences, in the 

 cells of various Algae, the mucilaginous layer is retracted, 

 in places or entirely, from the wall, and produces a mem- 

 brane on the surface, which becomes free, and bounded 

 externally by water. This membrane is not merely similar 

 to cell-membrane in outward conditions. It presents it- 

 self as such in all its characters, so that, in particular, it 

 has the power of growing out, either to produce a radical 

 hair (Bangid), or a new ramifying and fructiferous fila- 

 ment (Achlya). 



Even mucilage, mixed with various other contents, 

 which had escaped from injured Algae-cells into water, 

 and lay scattered in detached portions in this, sometimes 

 presented to me a bounding layer on the surface, which I 

 could not distinguish from the delicate membrane, such as 

 occurs on young cells. This bounding layer is wanting 

 to mucilage which has just escaped from the injured cell. 

 It is evident that it was produced by the mucilage. 



These three facts prove, that organic, unazotized mole- 

 cules are secreted on the surface of living vegetable mucilage, 

 and these inclose the mucilage in the form of a membranous 

 layer* Whether mucilage be free or lie in contact with 



* I here presume to add a remark on the term " mucilage" (schleim, 

 mucus). Most vegetable physiologists use the word, partly for vegetable 

 gelatine, partly for gum ; on the other hand, Schleiden applies it to the 



