OF SOUTH AUSTRALIA. 
305 
Subfamily Heterocladieae Decaisne. 
TKIGENEA Sonder. 
Fronds terete, subcartilaginous, laterally branched, ramuli slender, 
densely crested; thallus cellular, ramuli polysiphonous, corticated, consist- 
ing of a central siphon surrounded by four or five, concentric rows of cells, 
four in first row and more in outer rows, becoming smaller towards the 
periphery. Cystocarps sessile on the ramuli, globose, with a cellular peri- 
carp, osteolate; carpospores pyriform, fasciculate. Tetrasporangia in sub- 
clavate ramuli, single in each articulus, triangularly divided. 
Trigenea australis Sonder and Lehm. 
= Rhodomela trigenea Harvey. 
Frond 10 cm. to 20 cm. in length, cylindrical, inarticulate, cartilagineo- 
corneous, about 2 mm. thick, irregularly branched; the branches and stem 
densely clothed in every part with simple, or forked, filiform ramenta, 
1 cm. to 3 cm. in length, cartilaginous and inarticulate. A transverse 
section of a ramulus shows a small central tube surrounded by four or five 
concentric rows of cells, each of which contains a bag of chromule ; there are 
four cells in the inner row, eight in the next to it, 16 or 20 in the third, 
and those of fourth, which generally form the periphery, are very small 
and numerous. Cystocarps globose, membrano-cellular, pierced by a pore, 
sessile on sides of the ramenta, sometimes terminal. Colour brown-red. 
South Australia (Eastern Bays), West Australia, Victoria (Glenelg 
river) . 
Trigenea umbellata J. Agardh. 
Frond subumbellate, irregular ; the ramuli end in an umbel, bare below 
below the umbel ramelli shoot out raggedly ; the ramuli of the umbel carry 
either cystocarps or tetrasporangia in different plants. Colour purplish - 
red. Substance gelatinous, adheres to paper. 
South Australia (Encounter Bay, Eastern Bays), Victoria (Port Phillip). 
Fig. 145 . — Trigenia umbellata. 
