CELL-FORMATION. Ill 



with mucilage. When the cell expands more, it becomes 

 hollow in the interior. The mucilage remains on the wall 

 as a thin layer, and forms a coating over the whole inter- 

 nal surface. This is the mucilaginous layer which I have 

 described in the Alg8e,*and which Mohlf has named the 

 " primordial utricle" regarding it as a structure proper 

 to all cells. The mucilaginous layer is usually thicker at 

 the place where the nucleus of the cell lies, than over the 

 rest of the wall. Not unfrequently the nucleus lies 

 wholly imbedded in the mucilaginous layer. Schleiden 

 thought that it was inclosed in a duplicature of the cell- 

 wall. But this is certainly incorrect, and is best refuted 

 by the fact, that the nucleus may become detached, with 

 the mucilaginous layer, from the membrane of the cell. 



Mohl conjectures that the first thing formed around a 

 nucleus is the primordial utricle, and that the membrane 

 does not originate until after this. The statements in 

 regard to this are, however, too vague, and made without 

 consideration of cell-formation in the embryo-sac, so that 

 no minute discussion is necessary for the criticism of the 

 phenomena in question. I merely remark that I see the 

 origin of the mucilaginous layer (primordial utricle) on 

 the internal surface of the cell in the endosperm-cells, in 

 the same manner as in all other cells where new contents 

 are formed. The mucilage at first fills the whole cavity 

 of the cell, and subsequently merely lines the walls as a 

 thin layer. The mucilaginous layer is, therefore, a 

 secondary phenomena in the origin of the cell-contents. 



c. Of free cell-formation as a general law. 



Now that I have separately brought forward the facts 

 which are at my command respecting free cell- formation, 

 I will briefly collect and compare them, in order to 



* See Part I of this Essay. Ray Translation, p. 268. 

 t Botan. Zeit. 1844. (Translation in Taylor's Scientific Memoirs, vol. iv, 

 p. 91.) 



