Development, and Struetvre of the Vegetable Cell. l3l 



new tissue-cells, I have frequently seen that all the chlorophyll- 

 sacs lay completely continuous over the new septum. 



In this mode of multiplication of the joint-cells the nucleus 

 of the mother cells appears to be always absorbed, whilst new 

 nuclei make their appearance in the new joint-cells. 



I obser>ed this mode of development chiefly in .S. decimina 

 and S. nitidu. S. orthospira is less adapted to this purpose, on 

 account of the delicacy of the walls of its chlorophyll- sacs. For 

 my investigations I employed slides of very thin glass, so that 

 by turning them over I could examine the object on both sides, 

 with high powers, without disturbing its position. 



Figs. 59-61 represent different states of S. nitida during thU 

 septum-formation. 



In fig. 61 the two daughter cells, still destitute of nuclei, ant 

 somewhat contracted by dilute solution of glycerine, and covered 

 by the membrane of the secondary mother cell, which is like- 

 wise contracted. The chlorophyll-sacs, which at this period 

 frequently, although not always, lie parallel to the septum at 

 the point of contact of the two endogenous cells, are here, after 

 the contraction of the daughter cells, coiled up together over 

 the nucleus of their mother cell. 



In fig. 59 the nucleus of the mother cell was leen at a ia 

 course of ab9oq)tion, and fixed in the new septum, which was 

 surrounded on all sides by the chlorophyll-sacs. 



Fig. 60 shows a somewhat more advanced atai^e of develop- 

 ment: the new septum is here separated by the prolonged 

 action of water containing carbonic acid, into two laminae, the 

 thickening of which had commenced, not from the whole peri- 

 phery, but from one side. After the maceration of these cells 

 m solution of chloride of calcium, the portions of the primary 

 cells which were not vet thickened became much swelled, and 

 acquired a deep violet-\)lue colour with iodine. 



In the same specimens, as also in those cultivated with them, 

 m which I detected, in this way, with perfect certainty, the 

 multiplication of the joint-cells by endogenous cell-formation, I 

 likewise frequently obser\ed internal annular folds of the wall of 

 the joint-cell, and with far greater distinctness than in the cases 

 described in p. 125, as the folds here could be in general more 

 readily distinguished, from their considerable thickness, which 

 usually increases towards the central margin. 



When this folding existed in the lowest degree, the non- 

 nucleated daughter cells were developed in about the proportion 

 shown in fig. 61 ; between them the wall of the secondary mem- 

 brane of the joint-cell sank in, together with the unaltered and 

 regularly adherent chlorophyll-sacs, so far as to form a fold of 

 equal depth and breadth. 



9* 



