326 M. Miiller on the Development of Chara. 



Both however agree perfectly in being effected through cyto- 

 blasts. But I consider it hardly necessary again to bring for- 

 ward proofs of this kind of formation. They lie however, in the 

 absence of anything like a secondary, membrane, in each cell con- 

 taining cytoblasts, and in the existence of real, although very mi- 

 nute intercellular spaces ; hence the formation of new cells by 

 the contraction of secondary membranes, or from the deposition 

 of membranous matter upon projecting portions, as in Unger^s 

 view, is here quite out of the question. 



We shall now consider the cortical layer. In the further pro- 

 gress of the growth of the plant, the whorls of branches and of 

 shoots become separated from one another (figs. 12, 13). Be- 

 tween each whorl an internode is formed ; and if we trace this 

 process in its earliest condition, we find the cortical layer already 

 prepared, running from internode to internode : hence it must 

 happen that the number of utricular cortical cells is constantly 

 double that of the number of branches ; thus if there are six 

 branches, there are twelve cortical cells, &c. We do not find 

 any instances in which there is any great variation from the above 

 laws. Thus, in each cell of the branches, which is immediately at- 

 tached to the stem, two cytohlasts are usually transformed into two 

 new cells-, there is rarely only one present (fig. 17). Although 

 this process is very difficult to trace, I have directly observed it. 

 It is most easily followed by making extremely delicate longitu- 

 dinal sections through the axis of the plant ; we then find the new 

 cells with their cytohlasts, but always considerably turbid. In a 

 transverse section I have also found two cytohlasts in a cell, which 

 were on the very point of expanding into cells. These new cells 

 which are thus formed from cytohlasts now expand longitudinally, 

 and thus run in a longitudinal direction between the epidermoidal 

 membrane of the apex of the stem and the central utricle ; hence 

 they do not run externally but internally, being inclosed by the 

 membrane. In other respects their formation is similar to that 

 of other cells, as already described in the germinating plant. 

 Fig. 17. PL VI. represents a transverse section with the inter- 

 node cut through beyond its margin. This section, and such may 

 be frequently found, exhibits a central cell in its interior and seven 

 placed around it. These are provided with separating walls, and 

 divide the cavity of the stem into internodial cells. This is di- 

 stinctly seen in a longitudinal section, as in fig. 19. PL VII,, and in a 

 transverse section when made distinct by iodine, as in fig. 18, also 

 in fig, 15. Thus it is at the same time clear that the formation of 

 the cortical layer occurs upwards, and consequently resembles the 

 growth of the apex. The entire process however proceeds si- 

 multaneously with the development of the stem, the branches 

 and the shoots. Its cytohlasts are formed at the same moment 



