Polysiphonia of the Tropical Pacific, I — Hollenberg 
63 
type: D. 19116G2, cystocarpic, on Galaxaura 
sp., dredged 15 fa, Pokai Bay, Oahu, Hawaii, 
Aug. 1, 1959. It is represented by a glucose 
microslide. 
ADDITIONAL COLLECTIONS EXAMINED: HA- 
WAIIAN islands — D. 19144AX2, on other 
algae, dredged from 5-12 fa, Port Allen, Kauai, 
Sept. 12, 1959; D. 10821C, on a small boat 
just below the waterline, Kaneohe Bay, Oahu, 
Oct. 7, 1953; D. 19135Z4, tetrasporic, dredged 
from 26 fa, in front of the river, Waialua, 
Oahu, Aug. 2, 1959; tuamotu archipelago 
— D. 11514B, on Liagora sp. at a depth of 3-4 
ft in channels, south of Oneroa, and D. 
11857.31, on dead coral near Otetou, Raroia 
Atoll, legit M. S. Doty and Jan Newhouse, 
Aug. 5, 1952; marshall islands — D. 9456B, 
tetrasporic, on the under side of a coral head, 
Arno Atoll, Aug. 10, 1951; H. 48-1091.1, on 
H dime da sp., outer reef, Arji I., Bikini Atoll, 
July 12, 1948; H. 48-1 609C, tetrasporic, on 
Microdictyon, several miles north of Bikini I., 
Bikini Atoll, July 5, 1948; H. 48-1213.7, 
Amen L, Bikini Atoll, July 7, 1948; Caroline 
islands — D. 23032.5, on Microdictyon sp. on 
the reef between Ifaluk and Falalap islands, 
legit E. Menez, Aug. 10, I960. 
This species resembles P. anomala, which see 
for distinctive features. It also resembles P. 
tuberosa, from which it differs in having mostly 
unbranched erect branches. It lacks the tuberous 
food-filled rhizome frequently present in P. 
tuberosa. From P. tenuis it differs in being much 
more slender with much more reduced tricho- 
blasts and considerably smaller scar-cells. As 
many as 90 segments occur in the erect branches 
of D. 11857.31 beyond a lateral branch. 
Polysiphonia flaccidissima Hollenberg 
Plants to 3 cm high from limited prostrate 
branches, attached by unicellular rhizoids cut 
off as separate cells from the proximal end of 
the pericentral cells; erect branches mostly less 
than 15 Op in diameter and with segments mostly 
1. 5-2.0 diameters long; lateral branches mostly 
at intervals of 6-10 segments, arising in associa- 
tion with trichoblasts ; pericentral cells 4, ecorti- 
cate; trichoblasts delicate, unbranched or with 
1-2 dichotomies, one per segment in spiral 
series, tetrasporangia one per segment in slightly 
spiral series somewhat distending the segments ; 
cystocarps globular; spermatangial branches 
arising from a primary fork of a trichoblast, 
with or without a sterile tip. 
type locality: Laguna Beach, Orange 
County, California. This species, originally de- 
scribed (Hollenberg, 1942&: 783) from south- 
ern California, is a variable species of very wide 
distribution. 
P. flaccidissima var. flaccidissima Hollenberg 
(1942^:784) 
Figs. 2 A, 11 
Plants 1-3 cm high with limited prostrate 
portions; median parts of erect branches 100- 
110-(170)p in diameter and 1.0-1.5-(2.5) 
diameters long; walls thin and hyaline; main 
axes relatively distinct with laterals more or less 
distichous, arising mostly at intervals of 6 seg- 
ments but often at intervals of 10 or more 
segments ; branches slightly narrowed at the 
base; trichoblasts associated with branches un- 
branched or with 1-3 branches and up to 365p 
long ; scar-cells on both erect and prostrate 
branches; reproductive structures characteristic 
of the species, but the spermatangial branches 
generally lacking a sterile tip. 
type locality: Orange County, California. 
COLLECTIONS IDENTIFIED: HAWAIIAN ISLANDS 
— D. 19144T1, epiphytic, Port Allen, Kauai, 
dredged 5-13 fa, Sept. 12, 1959; M. 737, (as 
key to the varieties of Polysiphonia flaccidissima 
1. Erect branches mostly less than 1 cm high and less than 70p in diameter 2 
1. Erect branches mostly over 1 cm high and more than 70p in diameter var. flaccidissima 
2. Lateral branches infrequent var. lopi 
2. Lateral branches at intervals of 4-10 segments 3 
3. Lateral branches mostly at intervals of 10 segments, prostrate branches well developed . . . var. decimera 
3. Lateral branches mostly at intervals of 4-6 segments, prostrate branches absent or poorly devel- 
oped var. iki 
