Herposiphonia of Tropical Pacific — Hollenberg 
547 
In the branching pattern and the numerous 
segments in the determinate branches this spe- 
cies is similar to H. pacifica. From that species 
it differs in the relatively stiff determinate 
branches, with mostly shorter segments, but 
chiefly in the almost complete absence of trich- 
oblasts. The tendency of the determinate 
branches to remain slightly arcuate at maturity 
and the bluntly rounded apices of the deter- 
minate branches are additional features distin- 
guishing H. dubia. 
Herposiphonia plijera sp. nov. 
Figs. 2D, 10 
Saxicolous algae with prostrate indeterminate 
branches 60-80p in diameter, composed of seg- 
ments about 1 diameter long and attached by 
frequent unicellular rhizoids ; determinate 
branches erect, unbranched, up to 6 mm high 
and 4 5-6 5 p in diameter, with up to 57 seg- 
ments, mostly 1. 5-2.0 diameters long in median 
parts of mature branches; pericentral cells 12- 
14, central cells considerably larger, somewhat 
barrel-shaped, and with nearly as many chro- 
matophores as the pericentral cells; 3 determi- 
nate branches in alternating positions between 
successive indeterminate branches, with no bare 
nodes ; chromatophores frequently zonate ; trich- 
oblasts one per segment on the terminal 10- 
14 segments, alternately to pseudodichotomously 
branched 4-5 times, ultimately up to 500p 
long, arising in spiral sequence, with y 5 to % 
divergence, somewhat tardily deciduous, leaving 
relatively small scar-cells on the branches, which 
are ultimately frayed at the attenuate apices; 
tetrasporangia 45-5 5 p in diameter, tetrahedrally 
divided, in straight series of 15 or more toward 
the branch apices, not much distending the seg- 
ments ; cystocarps terminal, ovoid-globular, 240- 
373p in diameter; spermatangial stichidia in 
terminal, spiral series of 4 or more, wholly re- 
placing trichoblasts, each lanceolate, and slightly 
to markedly arched toward the apex of the bear- 
ing branch, at maturity about 115p long and 
l6p in diameter at the base. 
Algae tres ramos determinates erectos inter ramos 
indeterminatos successivos habentes; rami determinati 
usque ad 6 mm alt., plerumque 4 5-6 5 (x diam., c. 12 
cellulas pericentrales habentes, et e segmentis usque 
ad 57, 1. 5-2.0 plo longioribus quam latis in partibus 
mediis, compositi; chromatophora vulgo zonata; trich- 
oblastae in 10-14 segmentis terminalibus, plerum- 
que una in omni segmento, sitae; pseudodichotome 
4-5 ramosae, postremo usque ad 500p, long., in spira 
orientes, tarde deciduae; tetrasporangia 15 vel plura 
in serie versus apices ramorum, segmenta parum dis- 
tendentia; cystocarpi terminales, ovoido-globulares, 
ad 375jx diam.; stichidia spermatangialia multa, pro 
trichoblastis omnino substituta, lanceolata, paululum 
arcuata, ad 115p long. 
TYPE collection: T. 779-5, cystocarpic, in 
basalt tidepools, near Onenoa, Tutuila I., Ameri- 
can Samoa, legit R. Buggeln, Aug. 13, 1964. 
Represented by a glucose slide mount and fluid- 
preserved material. 
ADDITIONAL COLLECTIONS EXAMINED: AMER- 
ICAN Samoa — T. 770B, tetrasporic, 772, sper- 
matangial, on wave-dashed basalt shore, Ofu 
I., Manu’a group, legit R. Buggeln, Aug. 14, 
1964; maldive islands — Ha. 5-2B-119A- 
45B, tetrasporic, outer reef flat at a depth of 1 
ft, south and southeast of Imma I., Male Atoll, 
Mar. 21, 1964; Ha. 30-2Q-19A, cystocarpic, at 
a depth of 3 ft, Bushy I., Addu Atoll, May 10, 
1964; WESTERN ATLANTIC ocean — all previ- 
ously identified as H. tenella\ M. A. Howe 79 
(N.Y.), tetrasporic, in littoral zone on Rhizo- 
phora roots near Hamilton, Bermuda Islands, 
June 22, 1900; M. A. Howe 4100(N.Y.), in a 
tidepool, Georgetown, Great Exuma, Bahama 
Islands, Feb. 24, 1905; M. A. Howe 4151 
(N.Y.), tetrasporic, on Rhizophora roots, 
Stocking I., Exuma Harbor, Bahama Islands, 
Feb. 21, 1905; a collection by William Ran- 
dolph Taylor, no. 48, tetrasporic, on the walled 
side of a moat, Garden Key, Florida, 1924; a 
collection by W. R. Taylor and A. J. Berna- 
towicz, no. 25, Richardson’s Cove, St. George 
I., Bermuda, Feb. 21, 1949; a collection by S. 
Bernard Lewis, no. A1073, Southwest Cay, 
Jamaica, June 1950. 
All of the Atlantic specimens cited above 
seemed clearly referable to H. plijera, having 
the same branching pattern, approximately the 
same number of segments in the determinate 
branches, a similar number of pericentral cells 
and length of segments in mature determinate 
branches, a more or less simultaneous elongation 
of the segments of determinate branches, and 
numerous, relatively persistent trichoblasts of 
similar aspect, as well as other minor features. 
