232 
PACIFIC SCIENCE, Vol. XII, July, 1958 
Exogenous monosiphonous branches ap- 
pear on about the sixth or seventh segment 
removed from the apical cell (Figs. 2, 5). 
Boergesen’s figure (1919: 336, fig. 335) shows 
the monosiphonous branches as arising at 
about the tenth to fourteenth segment in his 
species, C. arcuata. With Bermuda materials of 
C. arcuata , provided by A. J. Bernatowicz, we 
have been able to confirm this observation. 
Boergesen also describes and figures the mo- 
nosiphonous branches as arising on the convex 
side of the branch endogenously. In the 
Bernatowicz collections cited, the tips curve 
and the branches appear on the convex side, 
the branches then become reflexed or curved 
in the other direction so that at maturity the 
branches do indeed protrude from the con- 
cave surface. 
These uncorticated exogenous branches are 
about 20 microns in diameter and, while the 
basal cell hardly becomes more than twice its 
diameter in length, the other proximal cells 
of these ultimately 14- to 16-celled branches 
become up to 5 times as long as broad (Figs. 
1, 2). The cells of the distal portion of these 
more or less determinate branches become 
progressively shorter distally until they are, 
just beneath the apical cell, discoid in imma- 
ture branchlets with hemispherical apical cells, 
or elongated and tapered toward the slender 
conical apical cell of a mature branchlet. 
The basal cells of the uncorticated exoge- 
nous branches are attached by their primary pit 
to the anterior-ventral corner of a lateral 
pericentral cell. They occur alternately on the 
right and left lateral pericentral cells of suc- 
cessive segments (Fig. 5). Secondary pits are 
formed in abundance between this basal cell 
and at least the lateral pericentral cell in the 
next anterior segment (Fig. 8) . At least one of 
these secondary pits may be unusually large 
(see Fig. 8). 
The older exogenous branches apparently 
drop off as the axes develop. Boergesen 
(1919: 147, fig. b) notes that exogenous 
branching was very rare in C fusiformis. He 
illustrates them, however, as exogenous at 
least once. According to Papenfuss (1944: 
207), of the Delesseriaceae, only Taenioma and 
Caloglossa have exogenous branches. On this 
point our organism seems to be more rhodo- 
melaceous than delesseriaceous. 
The rhizoids are exogenous and appear sev- 
eral segments posterior to the level at which 
endogenous branches appear (Figs. 1, 2, 8). 
They do not appear until after the other 
branches have appeared. They appear only 
from dorsal pericentral cells in our material. 
Sometimes a segment will bear one of each of 
the three types of branch. The rhizoids (Figs. 
2, 8) become separated from the parent peri- 
central cell (Fig. 2) at an early age and may 
become a few cells in length (Fig. 8) . There is 
a tendency for the rhizoids to be curved. Their 
tips become a disc of rows of small, crowded 
cells, connected by pits, that in some instances 
seem to have arisen by sympodial develop- 
ment (Fig. 8). In at least one case this pad 
was stuck to the Polysiphonia with which it 
was found entangled. 
The tetrasporangial stichidia arise endo- 
genously in the same positions as do endo- 
genous vegetative branches and appear to take 
their place. The discoid segments cut off by 
the apical cell of the stichidium usually elon- 
gate to about one third of their diameter be- 
fore cutting off a pericentral cell (Figs. 3, 4, 9). 
This usually occurs at the level of the first or 
second discoid cell. The first pericentral cell 
appears to be either dorsal or ventral; each 
situation was found with about equal fre- 
quency. Only a few rather disarranged branches 
were available for study of this point, how- 
ever. The other three pericentral cells appear 
very rapidly and are usually present on the 
second or third discoid central cell segment. 
The younger pairs of tetrasporangia arise 
towards the apex of the stichidium (Figs. 3, 9). 
The lumen of the tetrasporangium is radially 
elongated at least to a length of 60 microns at 
maturity, while the diameter parallel to the 
stichidial axis is about 47 microns. The tetra- 
spores (Fig. 9) are tetrahedrally arranged. 
The lateral pericentral cells each serve as 
