Herposiphonia of Tropical Pacific — Hollenberg 
543 
nodes devoid of branches, others having 1-4 
bare nodes between successive branches. From 
H. tenella it differs in being more slender, usu- 
ally with fewer pericentral cells, but differing 
especially in the position of the sexual structures, 
which arise mostly in the lower part of the 
branches rather than in the upper part as in H. 
tenella. Frequently the branching pattern 
changes in a given branch, so that no bare nodes 
occur in one portion of a branch, but one to 
several in another part, a feature reported to 
occur in H. tenella also. 
Herposiphonia dendroidea sp. nov. 
Figs. 1 C, ID, 1 E, 9 
Epiphytic or saxicolous algae with prostrate 
indeterminate branches 95-1 20p in diameter, 
composed of segments mostly about 1 diameter 
long, attached by numerous rhizoids with digi- 
tate and frequently multicellular tips; 3 deter- 
minate erect branches 50-70p in diameter in 
alternating positions between successive alter- 
nating indeterminate branches, with usually no 
bare nodes; pericentral cells 8-10; central cell 
at least twice the diameter of the pericentral 
cells ; mostly 7-9 segments in determinate 
branches, with segments mostly less than 1 
diameter long ; chromatophores zonate ; 2 
trichoblasts on the determinate branches, one a 
short terminal one on the much reduced ter- 
minal segment, which is slightly deflected in the 
direction of the apex of the related indetermin- 
ate branch, and a much larger one, apparently 
terminal but in fact subterminal on the second 
segment from the branch apex; young tricho- 
blasts with a prominent percurrent axis, the 
larger one 90-1 00- (800) p long with 5-6 lat- 
erals alternately inserted on the axis, not disti- 
chously, but directed, at least in early stages, 
toward the smaller trichoblast; basal cell of the 
larger trichoblast up to 240p long and 60p in 
diameter at maturity, the percurrent axis be- 
coming obscure ; tetrasporangia in straight series 
in the upper parts of determinate branches ; 
sexual reproductive structures not observed. 
Algae epiphyticae aut saxicolae, ramos indeter- 
minatos prostratos 95-120jx diam., segmentis aeque 
longis ac latis, habentes; rami determinati tres, nodi 
nudi inter ramos indeterminatos successivos plerumque 
nulli; cellulae pericentrales 8-10; plerumque 7-9 
segmenta in ramis determinatis, saepissime breviora 
quam lata; chromatophora zonata; duae trichoblastae 
in ramis determinatis, una terminali brevi in segmento 
terminali multum reducto qui ad apicem rami fertilis 
indeterminati paululum deflectit, et una multo maiore, 
ut videtur, terminali, subterminali, vere, autem, in 
segmento penultimo sita; trichoblastae iuvenes axem 
percurrentem perspicuum habentes, trichoblasta maior 
90-1 00- ( 800 )p long., 5-6 ramulis lateralibus prae- 
ditae; tetrasporangia in serie recta, in partibus super- 
ioribus ramorum determinatorum nata; structurae re- 
productivae sexuales non observatae. 
type collection: D. 11125.1, tetrasporic, 
abundant on dead coral beyond the reef ridge, 
transect area, Ngarumaoa I., Raroia Atoll, Tua- 
motu Archipelago, legit M. S. Doty and Jan 
Newhouse, July 8, 1952. This collection is rep- 
resented by two glucose slide mounts and fluid- 
preserved material. 
ADDITIONAL COLLECTIONS EXAMINED: PHOE- 
NIX islands — L. 2333.5, on Dictyosphaeria 
sp., Howland I., Oct. 10, 1964; L. 2532.4, in 
algal turf, north shore of Gardiner I., Oct. 23, 
1964; L. 2644.4, on Halimeda sp., Birnie I., 
Nov. 8, 1964; L. 2685.4, in algal turf at a 
depth of 3 ft, northeast reef, Enderbury I., Nov. 
11, 1964; tuamotu archipelago — legit M. 
S. Doty and Jan Newhouse, Raroia Atoll (16° 
S, 142° 26' W), 1952; D. 11160.4, on dead 
coral, reef near lagoon pass, July 9; D. 11508B, 
on other algae, Oneroa, near Pakakota, Aug. 5 ; 
MARSHALL islands — H. 48-1213.18, Amen I., 
Bikini Atoll, July 7, 1948. Plants of the last 
named collection had mostly 1-2 bare nodes 
between sucessive indeterminate branches. 
A variant form of this species is represented 
by D. 11858.8 in which only a single, strictly 
terminal trichoblast occurs on the determinate 
branches. These specimens were collected by 
M. S. Doty and Jan Newhouse near Otetou, 
Raroia Atoll, Tuamotu Archipelago, July 21, 
1952. 
Herposiphonia dendroidea var. minor var. nov. 
Figs. 7, 24 
Epiphytic algae with the general features of 
the species, especially as regards trichoblasts, but 
much smaller, having determinate branches 
mostly 80-1 OOp high and 2 5—3 5 pi in diameter, 
with 6-7 pericentral cells ; determinate branches 
usually 3, between successive indeterminate 
