CHARACEM. 



287 



gradually slower towards the interior ; hence the spheres and globules which swim 

 in the thin rotating protoplasm tumble over one another, because they become 

 immersed at different spots in layers of different rapidity. Dependent on the direc- 

 tion of the current, the grains of chlorophyll are arranged in longitudinal rows on 

 the stationary layer, and are deposited so thickly that they form a stratum ; they are 

 absent only at the neutral lines (Fig. 20^, A, i). These neutral lines mark the position 

 where the ascending and descending portions of the rotating protoplasm of a cell 

 run side by side in opposite directions and neutralise each other, and where therefore 

 there is no motion. The direction of the rotatory motion in each cell stands in a 

 regular relation to that of all the other cells of the plant, and hence to its morpho- 

 logical structure, as has been shown by A. Braun. 



With regard to the various processes of development, I will here describe only those 

 of the Globules and Nucules. 



Globules. The order of development of the cells has already been exhaustively de- 

 scribed by A. Braun in the case of Nitella symcarpa and Chara Baueri ; it agrees with that 

 of Nitella flexilis and Chara fragilis. In Nitella the terminal cell of the leaf becomes 

 the globule ; the oldest leaf of a whorl first forms its globule, the others follow 

 according to their age ; the globules are recognisable even in the earliest state of 

 the whorl of leaves. In Fig. 207, A^ is shov/n the longitudinal section through the 



KiG. 207.— Development of the antheridia oi Nitella flexilis. In R, C, and D the protoplasm has been 

 contracted by glycerine. 



apex of a branch, / being its apical cell ; its last-formed segment has already been 

 divided by a septum into a nodal mother-cell K and an internodal cell lying beneath it ; 

 beneath this lies the node with the last whorl of leaves ; b is its youngest leaf, bK the 

 basal node of the oldest leaf which already consists of the segments 7, //, ///; a is the 

 terminal cell of this leaf which becomes transformed into the globule. While the 

 globule is becoming developed, the leaf also undergoes still further changes which 

 must be first considered. The segment III becomes the first internode of the leaf, 

 7/ becomes a node from which are developed the lateral leaflets nb \x\ C and 7). The 

 cell 7 divides into two (C, 7), the lower of which remains short, while the upper grows 

 into a flask-shaped cell (Fig. 207, 7),/, and Fig. 208). 



The globular mother-cell of the globule (Fig. 207, A, a') first of all divides into 

 two hemispheres b.y a vertical wall passing through the axis of the leaf; these are 

 divided into four segments by a vertical wall at right angles to the first ; in each of the 

 four quadrants a third division takes place horizontally and at right angles to the two last 



