Herposiphonia of Tropical Pacific — Hollenberg 
549 
This species is similar to H. tenella in its 
slender form and pattern of branching. It differs 
from that species in having fewer pericentral 
cells and considerably longer and more slender 
segments in the determinate branches, but more 
especially in the lack of trichoblasts and in the 
point of origin of sexual reproductive structures. 
Herposiphonia oh s cur a sp. nov. 
Fig. 25 
Epiphytic algae with prostrate indeterminate 
branches about 10 Op in diameter, with 8-10 
pericentral cells and composed of segments 
mostly about 1 diameter long, attached by fre- 
quent unicellular rhizoids arising singly at the 
nodes ; apex of indeterminate branches only 
moderately inrolled; erect determinate branches 
with 8-10 pericentral cells and composed of 
mostly 7-20 segments, very variable in number 
in determinate branches on a given indeterminate 
branch, rarely by renewed apical growth with 
up to 85 segments; segments in determinate 
branches 0.5-1. 5 diameters long, with a diame- 
ter similar to that of the indeterminate branches ; 
each determinate branch followed distally by an 
indeterminate branch and 1—3— (5) bare nodes; 
indeterminate branch primordia mostly remain- 
ing very rudimentary, consisting of about 5 or 6 
cells representing the first very short segment of 
the branch; chromatophores not zonate; walls 
thin, usually brownish, dissepiments opaque ; 
trichoblasts 1-2, terminal, mostly absent or very 
rudimentary, rarely up to 300p long, with 3-4 
dichotomies; reproduction unknown. 
Algae epiphyticae, ramos prostrates indeterminatos 
c. lOOja diam., cellulis pericentralibus 8-10, apice 
modicius involuto, habentes; rami erecti determinati 
similes, cellulas pericentrales 10-12 habentes, et e 
7-1 8- (40) segmentis 8Q-90p diam., 0.5-1. 5 plo 
longioribus quam latis compositi; ramus indeter- 
minatus aut primordium rami et unus ad tres nodi 
nudi omnen ramum determinatum distaliter conse- 
quentes; primordia ramorum indeterminatorum max- 
ima ex parte semper magnopere elementaria, e c. 5-6 
cellulis, segmentum primum rami brevissimum ex- 
primentibus, constantia; chromatophora non zonata, 
membranis tenuibus, subbruneis, dissepimentis opacis; 
trichoblastae nullae aut rarae elementaresque, repro- 
ductio ignota. 
TYPE COLLECTION: D. 19645 Jl, epiphytic, 
dredged off Ewa Beach, Oahu, Hawaii, Feb. 
22, 1962.. This collection is represented by a 
glucose slide mount and fluid-preserved mate- 
rial. 
ADDITIONAL COLLECTIONS EXAMINED: HA- 
WAIIAN islands — D. 19H7B1, epiphytic, 
dredged at 25 fa, Pokai Bay, Oahu, July 30, 
1959; D. 19136K2, epiphytic, dredged at 16 fa, 
Waialua, Oahu, Aug. 2, 1959; D. 19645 Al, 
D. 19645L2, dredged off Ewa Beach, Oahu, 
along with the type collection ; line islands — 
D. 18995.1, on Halimeda sp., seaward reef flats, 
Christmas I., (1° 55' N, 157° 20' W), May 
16, 1962; D. 20022.1, on Halimeda sp., June 3, 
D. 20040, on coral, seaward reef flats, Christ- 
mas L, May 16, 1962 (all of the Christmas 
Island collections were made by Ralph F. Pa- 
lumbo) ; gilbert islands — D. 18937.5, epi- 
phytic, coral reef, Marakai L, legit Jane Cooper, 
July, 1962, identified by R. Tsuda (1964) as 
Polysiphonia fragilis Suringar ; maldive islands 
—Ha. 11-1D-122B-16, dredged at 25-35 fa, 
near Maduvari L, southwest boundary of Fadif- 
folu Atoll, Mar. 25, 1964. 
A collection by Leonard Horwitz, no. 9598a, 
from the lagoon side of Ine I., Arno Atoll, 
June- Aug. 1951, identified by E. Y. Dawson 
(1956:59) as Lophosiphonia hermudensis Col- 
lins and Hervey, is certainly a Herposiphonia 
and probably H. ohscura , judging by Dawson’s 
Fig. 65, in which the determinate branches are 
followed by the very rudimentary indeterminate 
branch primordia and then two bare nodes. The 
rhizoids arise from the morphologically distal 
end of the pericentral cells as seen by the relative 
positions of determinate and indeterminate 
branches. 
Due apparently to the thinness of the walls, 
plasmolysis of the cells of this species readily 
occurs in the dilute glucose mounting medium 
used. The central cells in this species are about 
the same diameter as the pericentral cells. The 
very rudimentary indeterminate branches con- 
stitute perhaps the most distinctive feature of 
this species. 
Herposiphonia pacifica sp. nov. 
Figs. 2 A, 2B , 4, 19 
Chiefly saxicolous algae, forming extensive 
turf or tufts up to 1.5 cm high; prostrate 
branches 100-170-(200)jx in diameter, with 
