425 
These secondary branches can be distinguished 
in the drawings of Harvey (Phye. brit. Plate 209) 
and KirzinG (Tab. phye. Vol. 13 Taf. 97 e, 98 e). 
They are very conspicuous in f. aculeata (fig. 374). 
As in other species of Polysiphonia, torsions 
may occur in the long branches with the con- 
sequence that the primary branches may be placed in 
a longitudinal row over a long stretch (Plate VI fig. 1). 
The central cell always contains a single 
nucleus; in the older cells it is rather large and 
situated in the middle of the cell. The pericentral 
cells after the formation of the secondary pits con- 
tain two nuclei which by continuous bipartitions 
produce the numerous small nuclei contained in 
the older pericentral cells. In one case c. 100 nuclei 
with a diameter of 5—6 4 were counted in one 
pericentral cell, while the nucleus of the central 
cell measured c. 30 x in the greatest diameter (fig. 
Fig. 369. 
Polysiphonia violacea. A, trichoblast. B, trichoblast with antheridia. 
200 : 1, 
Fig. 368. 
Polysiphonia violacea. A,cortical cell with three 
nuclei cut off from a pericentral cell. B, down- 
ward growing corlical filament on the point 
of establishing a secondary pit connecting it 
with another corticating filament. 230: 1. 
367). The central cell contains no 
chromatophores; the protoplasm 
shows a fine longitudinal striation. 
Cortical cells are always produc- 
ed, but the cortication occurs in 
various degrees; it is most developed 
in f. fibrillosa, least in f. fenuis. It is 
usually not more pronounced than 
that the pericentral cells are visible 
between the cortical filaments; in 
the lower part of the main stem, 
however, the pericentral filaments 
may be completely covered, in part- 
icular in f. fibrillosa. The primary 
cortical cells are cut off from the 
undermost part of the pericentral 
cells by oblique wall and 
originally contain more than one 
nucleus (fig. 368). They early be- 
gin to downwards in the 
outer wall two peri- 
central cells, dividing by transversal 
At their upper end they 
may also grow upwards 
segmentation. The descending bark- 
an 
grow 
between 
walls. 
under 
