gta 
or smaller. The thickness gradually increases towards over the middle, longitudinal divi- 
sions beginning at various distances from the base. The number of vertical septa in 
Fig. 613. 
Erythrotrichia reflexa. After living plants. In Bmonosporangia 
are to be seen. In C, the basis of the plant was hidden. D, 
monospores. After living plants. 340 : 1. 
each joint of the middlemost part of 
the frond may be about 4. Near the 
top the filament is again tapering; 
longitudinal divisions are wanting. 
As nearly all the observed spec- 
imens were unbranched, it appeared 
doubtful whether the Danish spec- 
imens ought to be referred to CROUAN’s 
species. One specimen only was found 
which showed a little branch issuing 
near the base (fig. 613 C). According to 
CrouaAN the fronds are branched or 
simple, with branches arising near the 
base, alternate or opposite. 
The young plants are cylindrical, 
monosiphonous, fixed to the substratum 
(various Algæ) by rhizoids produced 
by the lowermost cells of the filaments 
(fig. 612 B) and forming a conical 
attachment organ composed of several 
closely united branched cell-filaments 
(fig. 612, A, C). Crouan described the 
“root” as colourless; I found it of the 
same dark purple colour as the upright 
filament. Each cell of the filaments con- 
tains a stellate chromatophore with a 
central pyrenoid and long, simple or 
dichotomously branched arms bentalong 
the vaulted outside of the cell. In the 
polysiphonous portion of the frond the 
central part of the chromatophore is 
more or less approached to the outside 
of the cell. 
The sporangia (gonidangia) are 
cut off by longitudinal or somewhat 
oblique walls from cells in the poly- 
siphonous part of the frond (fig. 613). 
They are a little smaller than the vegeta- 
tive cells, about 14—16 w in greatest diameter, often broadly obovate, and are easily 
recognizable by their dense contents. The stellate chromatophore is not so distinct 
