Polysiphonia of Tropical Pacific — Hollenberg 
201 
branches commonly well developed, as much as 
2 mm long and 28-40p in diameter at the base, 
with mostly 3-5 dichotomies, the final branches 
tapering to delicate tips; trichoblasts arising one 
per segment on erect branches, with 2 pericen- 
tral cells and approximately 1/4 spiral turn be- 
tween successive trichoblasts, mostly soon de- 
ciduous but often relatively persistent, leaving 
small scar-cells and prominent wall-scars at the 
point of abscission; scar-cells on prostrate 
branches often 2 or more segments apart; tetra- 
sporangia 5 0-65 (i in diameter, in spiral se- 
quence in the tips of erect branches, not much 
distending the segments; sexual plants un- 
known. 
type locality: Key West, Florida. 
COLLECTIONS EXAMINED: HAWAIIAN ISLANDS 
— D. 18713, Midway I., legit C.H. Lamoureux, 
Oct. 6, 1962; D. 19127U, dredged 10-14 fa, 
Pokai Bay, Oahu, July 30, 1959; marshall is- 
lands — D. 9691.1 tetrasporic, D. 9692 A, tetra- 
sporic, D. 9696 A, lagoon reef drop-off, Ine 
Village, Arno Atoll, legit Leonard Horwitz, 
Aug. 22, 1951; H. 48-0290.2, inner reef, Eric 
L, Bikini Atoll, July 13, 1948; H. 48-0914.18, 
on Pocockiella sp., outer reef, Uku I., Bikini 
Atoll, July 9, 1948; H. 48-Y58.2, on dead 
coral, Biijiri I., Eniwetok Atoll, July 26, 1948; 
H. 48-Y72, on other algae, Runit I., Eniwetok 
Atoll, July 27, 1948; Caroline islands — all 
legit E. Menez, Aug. I960: D. 15413.1, D. 
15416.1, on Hypnea sp., eastern part of Helen 
Reef, Aug. 28, I960; D. 15897.8, tetrasporic, 
on dead coral, reef at Quoi I., Truk I., Aug. 1, 
I960; D. 23187.2, D. 23751.2, D. 23756.2, on 
coral and on other algae, Quoi I., Truk I., Aug. 
2, I960; D. 23565, tetrasporic, on other algae, 
reef of Iwayama Bay, Palau I. (7°20'N, 134° 
31'E). 
Examination of a fragment of the type, 
W.H.H.24, kindly sent from the Harvey 
Herbarium at Trinity College, Dublin, by Hilda 
Parks, reveals features which in detail corre- 
spond closely with those of the Pacific speci- 
mens, leaving little room for doubt concerning 
the identity of the latter, even though they are 
considerably smaller and with fewer lateral 
branches than the type. Another minor differ- 
ence may be mentioned. The central cell is rela- 
tively small in the type material but is usually 
nearly twice as broad as the pericentral cells in 
the Pacific specimens. 
A specimen which seems to be a variant of 
P. exilis is represented by D. 18713, collected 
by Charles H. Lamoureux, Midway L, Dec. 16, 
1962, cast ashore following a heavy storm. The 
erect branches are unbranched and slightly 
smaller than those of other Pacific specimens of 
P. exilis. There are 14 pericentral cells. Tricho- 
blasts tend to occur at intervals of 2-4 segments 
rather than on every segment, as is typical for 
the species. The plants were sterile. 
Polysiphonia homoia Setchell and Gardner 
1930:162; Hollenberg 1961:356 
Fig. 2 B 
Plants flaccid, epiphytic, to 3 cm high, at- 
tached by a basal tuft of unicellular rhizoids, 
mostly with digitate tips and cut off by cross- 
walls from an original basal cell (spore?) and 
from adjacent pericentral cells; 5 pericentral 
cells, ecorticate, with walls thin and hyaline ex- 
cept near the base, and with segments in main 
axes to 2.5 diameters long and with clear dis- 
sepiments; main axis 100-420p, in diameter, 
of segments 1.5-2. 5 diameters long; branches 
arising in connection with trichoblasts, at inter- 
vals of mostly 6-12 segments, slightly narrowed 
at the base; branching mostly pseudodichoto- 
mous; trichoblasts at irregular intervals, mostly 
2-3 segments apart in y 5 spiral sequence, up to 
400-550p long with 4-6 dichotomies and 
slender tapering tips, with basal cell very short 
and with the cell next to the basal cell about 
15(1 in diameter and up to 6 diameters long; 
tetrasporangia to 55p in diameter, in short 
slightly spiral series, not much distending the 
segments; cystocarps slightly ovate to nearly 
globular and 200-240ji in diameter, with osti- 
olar cells prominently enlarged at maturity in 
comparison with cells immediately below them; 
spermatangial branches measuring 200-275 X 
40-45(1, arising as a primary fork of a tricho- 
blast, without sterile tip. 
TYPE locality: Guadalupe L, Lower Cali- 
fornia, Mexico. 
Central Pacific collections are from the 
Hawaiian Islands only: D. 19144C1, on Galax - 
aura sp. dredged 6-13 fa, Port Allen, Kauai, 
Nov. 12, 1959; D. 19104E1, and D. 19104F1, 
