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THE SEAWEEDS 
thallus of the female gametophyte, more prominent on one side. Sporangia 
scattered over the surface of the sporophytic thallus in the outer layer, 
zonately divided. 
The family includes only one species, Rissoella verruculosa, not recorded 
from South Australia. 
Family RHABDONIACEAE. 
The thallus belongs to the central filament type. Of the four genera in 
this family, Catanella and Erythroclonium have a two-edged, and Rhab- 
donia and Areschougia a three-edged apical cell. From the apical cells 
branched short-filament systems are formed, which develop into the cortex. 
Rhizoids are present in the interior of the thallus of all Rhabdoniaceae, in 
small amount in the forms with inflated thalli, but to a very large extent 
in forms with solid thalli. 
The Solieriaceae and Rhabdoniaceae possess two common characteristics; 
firstly, the carpogonium and auxiliary cell are separated from one another, 
and therefore no procarp is formed, and, secondly, the first gonimoblast 
cell develops inwardly. However, the Solieriaceae thallus is of the '“foun- 
tain” type while the Rhabdoniaceae thallus is of the central filament type. 
The carpogonia develop from the central or inner cells of the cortical 
tissue, and are usually two to three celled, but may be branched. After 
fertilization the carpogonium develops one or two compound filaments. The 
auxiliary cell unites with a normal thallus cell in, the interior of the cortical 
tissue, and after fusion with a compound filament a first gonimoblast cell 
separates on the inner side, and this forms a crowd of filaments, which 
derive nourishment through the fusion cell. The cortex contains a fairly 
narrow osteole. The carpospores sometimes germinate in the cystocarp. 
Erythroclonium Sonder. Rhabdonia Harvey. Areschougia Harvey. 
Family RHODOPHYLL1DACEAE Kylin 1932. 
Plant plane or bushy, subsimple or branched; growth originating from 
a distinct apical cell, producing an evanscent primary axial cell row 
covered by an obscurely filamentous cortex; when mature the medulla 
either diffusely filamentous or apparently parenchymatous, the cortex of 
larger cells within, smaller without ; procarps present, the carpogenic 
branches of three cells, each with an auxiliary borne on the same supporting 
cell, the auxiliary equivalent to a segment of a corticating cell series; cysto- 
carp developed from the lobed enlarged auxiliary; pericarp formed by 
active division of the cortex about the developing cystocarp. 
Rhodophyllis Kutzing. Acanthococcus H. and H. Cystoclonium Kutzing. 
Family HYPNEACEAE Kylin 1932. 
Plants bushy, laterally branched, branches cylindrical, often with spinu- 
lose branchlets and crozier tips; structurally showing a central filament 
developed from an apical cell, and a filamentous cortex which matures into 
