Polysipbonia of the Tropical Pacific, I — Hollenberg 
59 
19. Mostly littoral plants, with branch apices not abruptly pointed; tetrasporangia protuberant (in certain 
varieties ) . . P. sphaerocarpa 
20. Rhizoids cut off by a, cross-wall from the pericentral cells 21 
20. Rhizoids remaining in open connection with the pericentral cells 25 
21. Mature rhizoids mostly with multicellular apices, arising at the distal end of the pericentral cells .... 
............................................................................... P. setacea 
21. Mature rhizoids unicellular, although often digitate, arising mostly at the proximal end of the peri- 
central cells ........................................................................... 22 
22. Erect branches regularly branched ..................................................... 23 
22. Erect branches mostly unbranched ...................................................... 24 
23. Branches arising apically in a typically exogenous manner; erect branches commonly 1 cm or more 
high P. upolensis 
23. Branches arising subapically in a delayed exogenous manner; erect branches mostly less than 1 cm high; 
prostrate branches frequently with tuberous portions .................................. P. tuberosa 
24. Segments of erect branches 1.2— 1.5 diameters long in median parts; trichoblasts at intervals of 1-2 
segments P. pseudovillum 
24. Segments of erect branches mostly 0.5 diameter long or shorter; trichoblasts at intervals of 4-8 or 
more segments ................................................................ P. quadrata 
25. Plants of mostly brackish water, mostly 3 or more cm high, with numerous branches ............ 
P. subtilissima 
25. Strictly marine plants, mostly saxicolous, and less than 1.5 cm high; erect branches simple or occa- 
sionally branched P. scopulorum 
Polysipbonia an o mala sp. nov. 
Figs. 1 A, 1 B t 1 C 
Extremely minute algae with creeping 
branches 3 0-40 p in diameter, composed of seg- 
ments 1.0-1. 5 diameters long, attached by fre- 
quent unicellular rhizoids, which are cut off as 
separate cells from near the center of the peri- 
central cells; erect branches arising cicatrigen- 
ously at frequent intervals, unbranched, to 1.5 
mm high but mostly much shorter, similar to 
the prostrate branches, but with segments mostly 
shorter than the diameter; pericentral cells 4, 
ecorticate; trichoblasts on erect branches rela- 
tively huge to 1.1 mm long, arising one per 
segment in J spiral sequence, with 3-4 dichot- 
omies and long tapering tips, mostly soon shed; 
scar-cells relatively large, 9-1 Ip in diameter, 
occurring one per segment in 4- spiral sequence 
on prostrate as well as erect branches; tetra- 
sporangia in short spiral series in the terminal 
parts of erect branches, which are prominently 
distended in fruiting segments ; cystocarps ovate 
to slightly urceolate, 1 2 0-1 40 p in diameter, 
with cells of the ostiolar rim not much enlarged, 
arising terminally on very short erect branches; 
spermatangial branches unknown. 
Algae minutissimae, praecipue prostratae, ramos 
repentes 30—40jx diam., per rhizoidea unicellularia, 
ut cellulas discretas separata affixes, et ramos erectos 
cicatrigenosos, saepissime breviores quarn 1 mm alt., 
habentes; cellulae pericentrales 4, ecorticatae; tricho- 
blastae relative immensae, ad 1.1 mm alt., 3-4 
dichotomias habentes, una in unoquoque segmento in 
ramis erectis, cito deciduae; cellulae-cicatrices magnae, 
una in unoquoque segmento, in 1 spira in ramis 
prostratis erectisque; tetrasporangia in serie spirali 
brevi in ramis erectis brevibus; cystocarpi ovati ad 
paululum urceolatos in ramis erectis brevissimis 
terminales; rami spermatangiales ignoti. 
type: H. 48-1213.19, cystocarpic, growing 
on a species of Microdictyon, Amen I., Bikini 
Atoll of the Marshall Islands, July 7, 1948. 
It is represented by a glucose slide mount and 
fluid-preserved material. 
other collections: H. 65-105, from a 
depth of 1-2 m north of North L, Johnston L, 
legit R. S. Jones, Apr. 22, 1965 ; H. 48—1609. B, 
cystocarpic, from coral reef several miles north 
of the north end of Bikini Island, Bikini Atoll, 
July 12, 1948; D. 9608B, tetrasporic, on Lia- 
gora sp. legit Leonard Horwitz, Arno Atoll, 
Marshall Islands, July 1, 1951; L. 2628.7, tetra- 
sporic, on Halimeda sp., Phoenix L, Phoenix 
Group, Nov. 6, 1964. 
P. anomala is commonly found on species of 
Microdictyon along with P. delicatula. Both 
species are delicate creeping forms. P. anomala 
differs from P. delicatula in the much shorter 
erect branches, huge trichoblasts, and much 
larger scar-cells, and in the procarps and cysto- 
