OF SOUTH AUSTRALIA. 
421 
Family THOREACEAE. 
The thallus is of the “fountain” type, and a colourless central region 
and coloured outer region can be distinguished. The outer region is usually 
composed of unbranched assimilatory filaments, radiating in bunches from 
the central body. The central body is composed of filaments, mainly longi- 
tudinal at the periphery but more transverse in the centre. The masses 
of filaments, and the whole plant, are covered with mucous, only the long 
assimilatory filaments passing out through the mucous. The systematic 
position of the genus Thorea is much disputed. The species of Thorea are 
found in quickly running streams or rivers, but none have as yet been 
recorded from Australia. 
Family CHAETANGIACEAE Schmitz 1889. 
Plants of moderate size, erect and bushy of habit, soft in texture, some- 
times partly calcified; structurally multiaxial, the filaments in the centre 
developing lateral branches of the “fountain” type, the outer cells of 
which may be closely associated into a continuous epidermis; mono- 
sporangia absent from most genera, but sometimes present; spermatangia 
scattered over the surface of the plant as little cells in small groups; 
carpogenic branches three-celled, borne on inner forks of the lateral fila- 
ments, the cell below the carpogonium capable of originating nutritive cells; 
cystocarps immersed, the gonimoblasts developed from the carpogonium; 
pericarp of slender crowded filaments produced from the lower cell of the 
carpogenic branch, eventually forming a pore at the surface. 
Galaxaura Lamouroux. 
Family NACCAR1ACEAE. 
The plants belong to the central filament type. They form, in their 
existence in the sea, a series to some extent parallel to the fresh-water 
forms Batrachospermum and Lemanea. The thallus development is similar 
to Batrachospermum. A whorl of four pericentral cells is formed, which 
form groups of short, branched filaments, from the basal cell of which 
long thin rhizoids grow out and surround the strongly developed central 
axis. From the rhizoids develop assimilatory filaments, but in old plants 
of N accaria these are broken down and the cortex becomes the assimilatory 
organ. 
The carpogonia develop from the basal cell of the fertile short filaments, 
and are two or three celled. After fertilization the supporting cell and 
carpogonium unite, the gonimoblast filaments developing from the carpo- 
gonium. Outer filaments form a layer around the central filaments, and 
the end cells of crowded, upright, branched filaments in the centre form 
carpospores. 
