196 
THE SEAWEEDS 
B. — Frond hollowed or tubular. 
a. Tetrasporangia cruciately divided. 
1. Frond sac-like Gloiosaccion 
Harvey. 
2. Frond cylindrical hollow, with similar 
lateral prolifications Bindera Harvey. 
b. Tetrasporangia triangularly divided. 
1. Frond tubular, divided by transverse parti- 
tions ; pericarp osteolate Champia Desvaux. 
2. Frond tubular, constricted at nodes, peri- 
carp without an osteole Chylocladia 
Greville. 
3. Frond consisting of enlarged rounded 
hollow inflations connected necklace-wise 
by narrow solid isthmuses Erythrocolon 
J. Agardh. 
HYMENOCLADIA J. Agardh. 
Frond gelatinous-membranaceous, flattened, clistichously subdichotomous 
or pinnately divided, composed of cells in two strata, the inner or medullary 
of large rounded-oblong cells mingled loosely with smaller cells, the outer 
or cortical of extremely minute coloured cells arranged in moniliform 
threads at right angles to the surface. Cystocarps scattered over the frond, 
hemispherical, with a thick pericarp, and basal placenta and many small 
carpospores. Tetrasporangia rather large, triangularly divided (into 
tetrads). 
A genus mostly Australian with one other species each in New Zealand 
and South Africa. There are 10 Australian species. Of these five have 
already been recorded from South Australia. 
Section A. 
Species with terete or narrow compressed frond, dichotomous or with sub- 
pinnate branching from the margin. Cystocarps marginal. 
a. Main axis flattened, 5 mm. to 6 mm. wide. 
1. Lax, dichotomous, with wide angles and 
incurved branches, ultimate branches often 
secund II. dactyloides . 
Sond. 
South Australia (Fowler Bay). 
2. Branches distichous, pinnate, closely placed, 
very patent, long (to 25 cm.), tapering with 
acute apices II. gracilarioides 
J. Ag. 
b. Main axis mostly terete, 1 mm. wide. 
1. Branches patent, filiform, distantly dichoto- 
mous, ramuli divaricate and flexuose II. filiformis 
Champion Bay, Eucla. J. Ag. 
