114 



VEGETABLE CELLS. 



nates, which attracts a small portion of the mucilaginous 

 contents, and becomes wholly clothed by it : on the surface 

 of the mucilaginous layer the cell-membrane originates. 



In the other cases of free cell-formation, nothing can 

 be seen of nuclei during the whole process. Either no 

 nucleus really exists, or it withdraws itself from vision, 

 through relatively minute size, or agreement of density 

 with the density of the contents of the young celL In 

 the first case we must assume, that a definite portion of 

 the contents of the parent-cell may independently become 

 individualized and converted into a cell. In the second 

 case, the process would be the same as in the endosperm- 

 cells. In my opinion a rigid distinction must be made 

 between normal and abnormal cell-formation, in solving 

 this question. By normal cell-formation I understand 

 such as is necessarily connected with the vegetative and 

 reproductive processes in a plant, and which always pro- 

 ceeds according to laws definitely laid down for each 

 plant. By abnormal cell-formation, on the other hand, 

 I understand such as is not directly and necessarily con- 

 nected with the vegetative and reproductive processes, 

 and must always be regarded more or less as produced 

 by the action of external influences interrupting the 

 regular course of the life of the cell. 



As to the abnormal cell-formation in the cells of Algae, 

 I am convinced that no nuclei ever take part in it. For 

 this kind of cell-formation is united by every possible 

 intermediate stage, with a process in which the formation 

 of nuclei cannot enter into the question. In the first 

 part of this Essay* I have mentioned a partial formation 

 of membrane where, in consequence of disturbing external 

 influences, the mucilaginous layer is retracted in places 

 from the cell-wall, and becomes coated with new pieces 

 of membrane. This process is of course independent of 

 the influence of any nucleus. I, at the same time, stated 

 that the mucilaginous layer sometimes becomes detached 



* Ray Translation, pp. 268 et seq. 



