442 
shallow water. In a specimen from the deepest locality where the species has been 
met with, US, Store Belt, in 33—45 meters’ depth, 9—10 pericentral cells were found. 
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Fig. 396. 
Polysiphonia nigrescens. Young plant. 
The lowermost cell of the primary axis 
is the short primary rhizoid-cell fixed to 
the substratum ; the second has produced 
no pericentral cells but several rhizoids. 
The following joints have produced peri- 
central cells, the numbers of which are 
indicated by the respective joints. A 
vigorous branch of endogenous origin 
is given off from the lower end of the 
“third joint. 70:1. 
cells, but are sometimes confluent and show some resemblance 
to cells (fig. 398). 
The older parts of the long shoots are usually covered 
by a continuous cortex. The cortical cells arise as small cells 
cut off from the lower end of the pericentral cells. 
The antheridia, as in the other species, usually occupy 
the prineipal axis of the fertile trichoblast except the two first 
The number of the pericentral cells is for the rest 
rather variable in different parts of the same plant. 
In the sporelings the first joint after the primary 
rhizoid-cell has no pericentral cells but gives rise to 
numerous rhizoids; the following two or perhaps 
more have 4, and in the next following the number 
gradually rises to the number normal to the species 
(fig. 396). In the branches of the latest order, the num- 
ber may be much lower; in a tetraspore-bearing spec- 
imen I found it reduced to 6 (fig. 401 C). 
The pericentral cells usually contain numerous 
large starch grains. The nuclei were found situated 
at the inner and radial walls, not at the outer wall. 
The pericentral cells often contain peculiar star- 
shaped bodies with curved rays which are probably 
a sort of crystalloids (fig. 397 B). They take a brown 
tinge when treated with iodine. They are very resist- 
ent to chemical reagents; they were not dissolved 
by KOH, HCl and Eau de Javelle, nor by boiling 
water. They seem to disappear at a later moment, 
for in older pericentral cells they were not met with. 
The inner and radial walls of older pericentral cells 
are transversely striped. In a tetrasporiferous branch 
I found two nuclei in the central 
cells (fig. 401). At the level of 
the transversal walls between 
the joints, intercellular bodies 
like those described by me in 
Polysiphonia fastigiata as inter- 
cellular cuticular bodies (1884, 
p-10 (2), figs.11—14) occur; they 
occupy the angles between the 
central cell and the pericentral 
a” 
Fig. 397. 
Polysiphonia nigrescens. A, 
pericentral cell showing 
chromatophores {lying at 
the outer wall, January. 
435 : 1. B, star-shaped 
bodies, probably crystal- 
loids in pericentralZ cells. 
300 : 1. After living 
plants. 
