431 
blast; the first branch of the second order III! is a — AD 
directed towards the stem (fig. 376). Each cell of the GS SS CT 
trichoblasts contains one nucleus. For a transitional Aim Be C 
stage between a trichoblast and a stem comp. K. R. 
1903, p. 457. 
The number of pericentral cells is, as shown 2 [) 
by J. AGARDH, 7— 8, more rarely 6, in the full-grown > Co 
plant. The first pericentral cell is cut off exactly D E 
under the first leaf or, more frequently under its Fig. 377. 
right side (fig. 377). The cortication begins rather polysiphonia Brodiei. A—C, segregate young 
early, the primary cortical cells being cut off at the s¢éments of sporeling seen from the face, 
4 2 showing the successive divisions. D, E, 
lower angles of the pericentral cells and growing similar segments, from older plant, the 
downwards and dividing. A cortex of considerable fourth from the top, showing the relation 
; wa gg of the first pericentral cell to the tricho- 
thickness, consisting for a great part of hypha-like plast; D seen from above, E from below. 
filaments, early covering the pericentral cells, is then —% Youns segments seen from the side. 626:1. 
formed. At the same time a plexus of hypha-like 
filaments appears between the central cell and the pericentral cells (fig. 378). It was 
detected by J. AGARDH (1863, p. 993), who thought that it arose by division of the 
central cell. Later on it was figured by FALKENBERG who rightly shows (1901, 
p. 34, Taf. 21 Fig. 12) that the hyphæ arise from the pericentral cells, which I can 
confirm. Secondary pits are produced in considerable number through the longitudinal 
walls between the cortical 
cells mutually and between 
these and the pericentral 
cells. 
The branches arise, as 
shown by Kny (1873), in 
the axils of the trichoblasts, 
however, not exactly in the 
median plane, but they are 
somewhat displaced to the 
left. The joint common to 
5) 
ORs 
VÆK A 
HX > < i i 
: the trichoblast and the 
Fig. 378. branch has 3 pericentral 
Polysiphonia Brodiei. Transverse sections of stem. A rather young. 200: 1. 
B older with hypha-like filaments in the interior of the stem. x the central 
cell. 63:1. situated to the left and one 
to the right of the median 
plane of the trichoblast, as shown by Kny. The pit connecting the second cell of 
the trichoblast with the central cell of the basal joint appears at the upper end of 
the longitudinal wall between the middlemost pericentral cell and that to the right 
(fig. 379). The ordinary (primary) branches do not arise in the axils of all the 
trichoblasts. In the lower part of the long shoots none or only few are present, upwards 
55* 
cells, two of which are 
