Polysiphonia of the Tropical Pacific, I — Hollenberg 
89 
omies; scar-cells small, frequently present on 
prostrate branches; wall-scars rarely present at 
the former point of attachment; tetrasporangia 
to 70p in diameter in spiral sequence in ulti- 
mate and subultimate branches; cystocarps 
globular, 2 5 0-3 5 Op in diameter, with cells of 
the ostiolar rim distinctly enlarged; sperma- 
tangial branches cylindrico-conical 140-170- 
(290) X 40-60p, mostly without sterile tips, 
arising as a primary branch of a trichoblast. 
type locality: St. Thomas Island in the 
Virgin Islands. As represented in the tropical 
Pacific Ocean this is a very variable species. 
It has been identified by Menez (1964) and 
other investigators as P. pulvinata (C. Agardh) 
J. G. Agardh (i.e., Hut chins /a pulvinata C. 
Agardh). According to Boergesen (1930:85), 
f( Hutchinsia pulvinata C. A g., and most prob- 
ably Conferva pulvinata Roth, both quoted by 
Montagne, have 6 pericentral cells, as pointed 
out by Bornet [1892:306], who probably ex- 
amined Roth’s specimens.” 
The writer examined five specimens from the 
Kiitzing herbarium identified as P. pulvinata 
C. Agardh. Cross sections showed that two of 
these have 6 pericentral cells. The other three 
have 4 pericentral cells. In none of the five 
specimens do the scar-cells occur regularly on 
each segment as in the various specimens from 
the tropical Pacific Ocean. One of those with 
4 pericentral cells bears the notation "a com- 
municat ex herbario J. G. Agardh.” 
The writer’s observations and those of Boer- 
gesen seem to indicate that the specimens here- 
with identified as P. sphaerocarpa Boergesen 
cannot be identified with P. pulvinata (C. 
Agardh) J. G. Agardh. 
Although Conferva pulvinata Roth has prior- 
ity, Roth’s specimens, unfortunately, are not 
available for study, having been destroyed dur- 
ing the second World War. On the other hand 
the writer examined a prepared mount and 
fluid-preserved material of the type of P. 
sphaerocarpa kindly loaned from the herbarium 
at the University of Copenhagen and found the 
Pacific specimens to agree in all basic details 
with the type of Boergesen’s species, although 
the Pacific plants exhibit much more variability 
than Boergesen’s description would indicate. 
Taylor (I960) describes P. sphaerocarpa as 
"a reef plant growing in exposed places.” Those 
so identified from the Pacific are of similar 
habitat. A number of collections by Dr. A. J. 
Bernatowicz from Bermuda, identified as P. 
sphaerocarpa, were found to correspond closely 
in most respects with the Pacific specimens, in- 
cluding the enlarged cells of the rim of the 
ostiole of the pericarp. 
P. sphaerocarpa as described herewith seems 
close to P. simplex Hollenberg (1942^:782), 
but the latter plant is often larger and is basically 
prostrate, with assurgent branches, whereas 
P. sphaerocarpa is tufted erect with limited 
prostrate branches. 
key to the varieties of Polysiphonia sphaerocarpa 
1. Segments in median parts of leading branches mostly about 0.5 diameter long; trichoblasts well devel- 
oped and relatively persistent var. ) dlifera 
1. Segments in median parts of leading branches mostly about 1 diameter long; trichoblasts mostly less 
well developed and soon deciduous 2 
2. Lateral branches abundant, at intervals of 5—12 segments var. sphaerocarpa 
2. Lateral branches commonly at intervals of 20 or more segments var. distans 
slide. 26, Polysiphonia sphaerocarpa var. sphaerocarpa, a variant form with enlarged spermatangial stichidia, 
with proliferating apices. 27, Polysiphonia sphaerocarpa var. filifera, with spermatangial stichidia. 28, Polysi- 
phonia sphaerocarpa var. filifera, tetrasporic. 29, Polysiphonia upolensis, vegetative branch tips. 30, Poly- 
siphonia scopulorum var. scopulorum, prostrate branch, with young erect branches and rhizoids, attached to a 
firm substratum. 31, Polysiphonia scopulorum var. scopulorum, prostrate branch, with young erect branches 
and rhizoids attached to a porous, soft substratum. 32, Polysiphonia rubrorhiza, erect branch tips, with 
cystocarps (type material). 33, Polysiphonia scopulorum var. scopulorum, tips of erect branches. 34, Poly- 
siphonia scopulorum var. minima, tips of erect branches bearing spermatangial stichidia (from the type col- 
lection). 35, Polysiphonia upolensis, tips of tetrasporangial branches, tetrasporangia in spiral series. 36, 
Polysiphonia scopulorum var. scopulorum, tips of erect branches with tetrasporangia in straight series. 
