66 BRITISH CHAROPHYTA. 



nuclei, as the result of the simple fragmentation of the 

 original nucleus, this fragmentation being brought 

 about either by a process of annular constriction or by 

 the appearance of a fissure in the interior of the 

 nucleus which extends to the exterior (see Sachs, 

 ' Lect. Physiol. PI./ TransL, p. 106). 



Most of the cells contain chlorophyll in the form of 

 minute granules, " chloroplasticls," disposed in rows 

 embedded in a stationary layer of protoplasm, the 

 " ectoplasm," lining the internal surface of the cell- 

 walls. In the vegetative parts the chlorophyll granules 

 remain green, in the cells of the antheridium in which 

 they are present they assume an orange or red colour at 

 maturity. The chlorophyll granules which are in a 

 single layer do not completely line the cells, there being 

 a neutral portion, appearing as a narrow spiral band, 

 from which they are lacking. This colourless band is 

 particularly noticeable in the long internodal cells. It 

 has been called the neutral or indifferent line. 



Cyclosis, or streaming, that is the rotation of proto- 

 plasm within the cell, which was first observed in a 

 Charophyte, is particularly well exhibited in these 

 plants, and may be seen in almost all fully-grown cells. 

 The cyclotic flow is in the form of a definite stream of 

 protoplasm within the ectoplasm, following the direc- 

 tion of the rows of chlorophyll granules, passing up 

 one side of the neutral line around the end of the cell 

 and down the other side. In the elongated lateral 

 members, such as the internodes of the branchlets and 

 the spiral-cells of the oogonium, the stream proceeds 

 upwards on the outer side of the cell, i. e. that farthest 

 from the axis of the stem or fruit, and downwards on 

 the inner side. The direction of the flow in each type 

 of cell was worked out by Alexander Braun and will be 



