THE VEOSTABLE CELL. ol 



While the filament ib becoming longer in this way, the membranes 

 of many of the older cells of the filament become protruded out 

 sideways at the upper end (%. 1, h), the process growing gra- 

 dually into a cylindrical branch (fig. 1, c) as large as a cell^ which 

 then becomes shut off at the base from the stem-cell, by a parti- 

 tion (fig. 1, d) ; then it presents the same elongation and the 

 same division in the middle (fig. 1, e) as the end cell of the stem 

 exhibits, thus producing a branch, which is capable of ramifying 

 again in like manner. 



So that consequently, there are never any small cells, which 

 would be required to grow, formed in these plants, but every cell 

 possesses fi'om the first very nearly the dimensions to which it is 

 subsequently fixed, only a slight growth in width occurring in it. 



The process of the formation of the septum is as follows : the 

 cells are lined by a primordial utricle, on the inside of which 

 lies a layer of chlorophyll gTanules (pi. 1 , figs. 5, 6), which by the 

 action of substances injurious to the life of the plant, such as 

 alcohol, acids, &c., are separated from the primordial utricle (fig. 

 5 a), while this also under the same circumstances becomes de- 

 tached from the cell- wall. At the place where the partition is to 

 be formed, an annular fold grows inwards, gradually contracting 

 and parting off" more completely the chlorophyll layer, which is 

 detached from the primordial utricle for some distance (fig. 5). 

 During tliis time a cellulose membrane is deposited all over the 

 outside of the primordial utricle (figs. 3, 4) ; so far as this lies be- 

 tween the outer surface of the primordial utricle and the inner 

 surface of the dividing cell, it constitutes the youngest and inner- 

 most of the secondary membranes of the latter ; but at the point 

 at which the primordial utricle forms the fold just described this 

 cellulose layer is continued into the duplicature of the fold, and 

 thus forms an annular, thin, imperfect septum composed of two 

 layers. This annular fold, and the cellulose membrane lying in 

 it, contract more and more upon the central orifice until this dis- 

 appears, the chlorophyll layer and the primordial utricle are cut 

 off* into two portions, and the cellulose membrane presents itself 

 as a perfect partition (fig. 6). Thus, without important disturb- 

 ance of the contents of the mother-cell, two secondary cells are 

 formed in it, which receive within them the whole contents, and 

 the membranes of which so far as they are in contact with the 

 membrane of the parent-cell serve as layers of thickening to^ it, 

 while where the secondary cells touch they appear as a partition 

 of the parent-cell. 



Ohserv. L I have given a somewhat detailed account of these pro- 

 cesses, because I believe that I have traced them more minutely than 

 others have done. KageH {'' EeitschrifC i. 98) thinks that my description 

 of the parting off of the cell-contents by a fold growing inwards in the 

 cell, is incorrect ; he denies to the pr-hnordial utricle the characters of a 

 membrane, and contends that it is a layer of mucilage, not sharply de- 



E 2 



