824 M. Miiller on the Development of Chara. 



posited. There are usually six of them, but sometimes seven, eight 

 or more. Hence, according to their number, the central cell is six-, 

 seven-, eight- or more sided, since they directly limit and com- 

 press it. They are themselves also naturally flattened at their points 

 of contact, but are spherical towards the exterior. If at this time, 

 as is usually the case, many layers of them are arranged together, 

 the central cell becomes a short, six- or more sided column ; the 

 cells surrounding it therefore possess only four longitudinal sur- 

 faces — ^the external of which are thus spherical, the three inner 

 flattened — and two transverse surfaces bounded by four sides. 

 Each cell contains a cytoblast. There are four perfect cells also, 

 having very delicate walls, on the apex of the bud. But exactly 

 at that part where they meet in the centre of the axis they inclose 

 a small and very pale body, which is the true vegetating point — 

 perhaps it is the newly forming cytoblast of the central cell. 

 This point is likewise of importance for the further formation of 

 the cellular tissue of the axial bud. 



The central cell is the commencement of the true stem, or, as it 

 is usually called, of the central utricle in all Charce provided with 

 a cortical layer. But the cells which surround it do not con- 

 stitute the commencement of this layer, but of the branch. 



As the plant elongates, of course the central cells also elongate 

 and form long tubes. At first lying close to the cells of the 

 branch they continue to become more expanded, especially when 

 they have acquired the cortical layer. Its cells then become 

 rounded both externally and internally, and thus the central utri- 

 cle appears distinct, whilst previously (fig. 18) it could only be 

 made perceptible by iodine, which coloured the delicate intercel- 

 lular spaces and the walls of the utricle blue. Thus it is trans- 

 formed from the cytoblastema into an amylaceous substance, 

 which subsequently becomes converted into membranous matter, 

 and is then no longer coloured by iodine. As soon as this hap- 

 pens the central utricle becomes considerably thickened by the 

 absorption of more nutriment, and it is very beautiful to see how 

 this is deposited in layers. Hence the stem of the perfect plant 

 differs considerably from that of the germinating plant in the 

 manner of its development. In the former it is primary — an im- 

 mediate expansion of the nucleus ; in the latter secondary, but 

 formed by a higher process. 



When the branches are about to form, the cells which surround 

 the central cell become expanded in the form of simple cylinders 

 (figs. II, 14). Internally they exhibit exactly the same struc- 

 ture as the axis, for we find the same central cells and external 

 cells also with extremely delicate walls already formed in them 

 (fig. 16). They also have a terminal bud, from which new cells 

 are formed as in the case of the stem. The principal difference 



