Brackish-Water Algae from Hawaii— Abbott 
Islands for the first time. It occurs com¬ 
monly on many marine algae in this area. 
Distribution: Occurring commonly in the 
tropics, epiphytic on littoral and sublittoral 
algae; extending into temperate waters as far 
north as England (type locality). 
Acrochaetium Nageli, 1861: 402 
The treatment of this genus is based on 
the work of Papenfuss (1945), who has 
seen our specimens. 
Acrochaetium robustum Boergesen, Mar. 
Alg. D. W. I., 2 (1): 40-43, 1915 (see 
Fig. Aa-b). 
Plants tufted, to 1 cm. in height, epiphy¬ 
tic, with a simple or branched basal cell 
partly to wholly endophytic. Branching pre¬ 
dominantly lateral, sometimes alternate, but 
at the base dichotomous. Cells with a parie¬ 
tal chromatophore and a single pyrenoid, 
and with pit connections readily seen. Cells 
to 4 fx in width, and twice as long. Mono¬ 
sporangia prominent, sessile or pedicellate, 
appearing laterally near the tips of the 
fronds, singly or in pairs. Terminal spo¬ 
rangia are often seen. Sexual organs not 
seen. 
Found in Kuapa Pond, epiphytic on Batis 
maritima, and a piece of coniferous wood. 
Not the same species as other marine speci¬ 
mens from this area. The genus is newly 
reported from the Hawaiian Islands. 
Distribution: Danish West Indies, Japan. 
Acrochaetium seriatum Boergesen, Mar. Alg. 
D. W. I., 2 (1): 32-35, 1915 (see Fig. 
Ac). 
Plants to 5 mm. in height, tufted, soft, 
epiphytic on Ulva fas data. Branching 
chiefly lateral, occasionally alternate. Erect 
portions arising from a multicellular creep¬ 
ing base. Monosporangia borne singly or in 
clusters, sessile or pedicellate. In Keawanui 
Pond, Molokai Island, on Ulva fas data. 
Distribution: Danish West Indies, Ma¬ 
cassar. 
203 
Both these species of Acrochaetium were 
collected in the more saline portions of 
Kuapa and Keawanui. In all probability 
they are not true brackish-water species. 
Species of Acrochaetium occur frequently on 
larger algae in the marine environment in 
this area. 
Gelidium Lamouroux, 1813: 40 
Gelidium pusillum (Stackhouse) Le Jolis in 
Soc. Sci. Nat. Cherbourg, Mem. 10: 139, 
1863 (see Fig. 5). 
Fig. 5. Gelidium pusillum (Stackh.) Le Jolis. 
Habit of portion of a plant. X 4. 
Plants small, associated loosely in clusters, 
with a creeping base bearing erect parts to 
3 cm. in height. Branching irregularly pin¬ 
nate or alternate, with both branches and 
axis markedly flattened. Rhizines occupy a 
large central area of the branches with small 
cortical cells in three rows on the outside. 
Tetrasporangia in small bulbous lateral 
branchlets, sunken below the surface. Tetra- 
spores in cruciate groups when mature, the 
