1278 Prof. H. Karsten on the Formation, 



This process occupies some few minutes ; and in order to observe 

 it the eye must be fixed upon some one such cell containing but 

 little chlorophyll, and in which the fold of the wall is fully 

 formed, though a septum be as yet not present in it. 



After the septum has attained the characters of a complete 

 disk dividing the cell-cavity, an act of growth, or at least an 

 expansion of the cell-wall, still goes on, whereby the rather 

 obliquely placed septum acquires a horizontal direction, and a 

 certain amount of pressure is at the same time exerted upon the 

 cell-wall, which forces apart or extends the fold (above which 

 the enveloping membrane is torn through), and thus enlarges 

 by about one-third of its length the mother cell of the two 

 newly developed cells (figs. 23 & 23). 



Contemporaneously with this sudden evolution of the mother 

 cell, the two endogenous cells undergo expansion. When both 

 these cells are not equally enlarged, it is, as a rule, the upper 

 one (usually the smaller of the two) which at first expands compa- 

 ratively more strongly, and at the same time downwards towards 

 the new septum, whilst the chlorophyll- and starch-vesicles, com- 

 pressed against the walls of the mother cell, do not at first 

 undergo very much displacement. This is the reason why, 

 at the first moment after the extension of the mother cell, the 

 new septum is usually found free from secretory vesicles, and 

 only bounded by a transparent watery fluid (Bary's colourless 

 layer), as happens also with the inferior extremity of the lower 

 of the two daughter cells. 



: This primary and abruptly accomplished enlargement of the 

 endogenous cells, after the laceration of the enveloping mem- 

 brane, is, like that of the mother cell itself, only a mechanical 

 act, — not a process of growth, but merely the extension of the 

 cell-wall already enlarged by assimilation. The secretion-cor- 

 puscles, however, gradually distribute themselves equally over 

 the whole surface — except that, quite at the upper end, at the 

 summit of the mother cell, a compact group of these secretion- 

 corpuscles remains, even in cells otherwise almost destitute of 

 such contents, whilst the lower extremities of the two young 

 daughter cells usually continue longest free from these sub- 

 stances, and appear colourless. 



Nevertheless, this distribution of the secretion-material is not 

 so rigorously subjected to the rule just mentioned as not to 

 admit of exceptions. 



These relations are, however, it appears to me, worthy of 

 notice, because they may furnish data for arriving at conclusions 

 respecting the place of formation of the secretory material, the 

 direction of the cell-growth, and therefore the direction or course 

 of the nutritive matters distributed in the series of cells. 



