Brackish-Water Algae from Hawaii— Abbott 
Plants erect to 20 cm. in height, or more 
usually matted and attached epiphytically to 
other algae, with slender branches alternate 
or whorled and closely beset with very short 
branchlets, the ultimate tips simple and 
straight. Plants red to reddish-green when 
fresh. In section, the main axis shows a large 
medullary layer surrounded by cortical cells 
in radial rows of smaller cells, and a some¬ 
what firm superficial layer of angular cells. 
Tetrasporangia circling the base of the short 
branchlets, the cortical cells forming distinct 
radial filaments in these areas. Sporangia 
zonately divided. Male and female plants 
not seen. 
Found in Ilae Pond, growing with Cera- 
mium spp., and Polysiphonia. In the Ha¬ 
waiian area, common in sandy shallow 
waters. 
Distribution: "ad insulis Sandwich.” Re¬ 
ported by Reinbold from the Hawaiian 
Islands, and from Malaya by Weber-van 
Bosse (1928: 453). 
Hypnea nidifica seems more closely re¬ 
lated to H. cornuta in habit than to H. cervi- 
cornis, a comparison made by J. Agardh. 
The anatomy of the frond is closer to the 
next species than to the two species just 
mentioned. Tetrasporangia are like those of 
most other species. 
The species has been listed by Chamber- 
lain, Lemmermann, Reed, Setchell, Rock, 
MacCaughey, and Neal. Hypnea armata has 
been listed by Reed, Rock, and MacCaughey. 
Hypnea cornuta, H. pannosa, and H. divari- 
cata mentioned by Chamberlain have not 
been verified. 
Hypnea nidulans Setchell, Veg. Tutuila 
Island, Carnegie Inst. Wash. 20: 161- 
162, 1924 (see Fig. 7c-d ). 
Plants smaller than H. nidifica, much 
twisted and branched, growing in small tufts 
among other algae. It is chiefly differen¬ 
tiated from H. nidifica in having tetraspo¬ 
rangia in nemathecia near the tips of the 
207 
fertile branchlets. In cross section, the cor¬ 
tical cells are smaller, with small uniform 
superficial cells. Only tetrasporangial plants 
were collected. 
Found in Molii Pond. Newly reported 
from the Hawaiian Islands. 
Distribution: Samoa (type locality), 
Setchell 1084, type, in U.C. Herb., Setchell 
and Parks 3138 in Herb. Bishop Museum. 
Also reported by Boergesen (1943: 62) from 
Mauritius and by Weber-van Bosse (1928: 
454) from Malaya. 
Fig. 9. Gracilaria coronopifolia J. Agardh. 
Habit of a portion of a cystocarpic plant. Natural 
size. 
Centroceras Kiitzing, 1841: 731 
Centroceras clavulatum (C. Agardh) Mon- 
tagne, Flore d’Algerie, 140, 1840-1850. 
Plants filamentous, usually in matted 
tufts, stiff and brittle, or floating and en¬ 
tangled with other algae; dark purplish-red 
in color, or pinkish where exposed. Fish¬ 
pond specimens are 6-8 cm. in height with 
irregular branching and short internodes at 
the tops of the branches, the tips sometimes 
forcipate. Spines at the nodes most prom¬ 
inent in the upper parts of the filaments, 
4 to 6; in the older parts usually 2 or de¬ 
ciduous. Spines are of two or more cells. 
Cortical cells in section, 28 to 40 in the 
nodal portions. Tetrasporangia sub-external, 
formed in a horizontal row of 4 to 8 at the 
nodes, tetrahedrally divided. 
