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THE SEAWEEDS 
Family GIGARTINACEAE Schmitz. 
Frond terete, two-edged, flat, foliaceons ; dichotomous, much branched, or 
lobed — in fact with all manner of contours. Composed of two or three 
distinct strata. Cystocarps prominent or immersed. Gonimoblast forming 
a clump, the branches of which are conjoined with the surrounding tissues, 
evolving the carpospores within the mass. Tetrasporangia more often 
cruciately divided. 
CONSPECTUS OF THE SUBFAMILIES.- 
A — Thallus traversed by a median axile fasciculus of 
longitudinal sometimes forked filaments. Thallus 
endowed most distinctly with a filamentous structure. 
Tetrasporangia mostly cruciately divided Gigartineae. 
B. — Thallus most rarely showing filamentous struc- 
ture. 
a. Tetrasporangia cruciately divided. Auxiliary 
cells situated at the outer limit of the cortex, 
bearing a three-celled carpogonial branch 
directed outwards Tilocarpeae. 
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b. Tetrasporangia zonately divided. Auxiliary 
cells situated in the interior region of the 
cortex, bearing laterally single or several 
three-celled carpogonial branches. 
1. Structure of frond filamentous-cellular . . Mychodeae. 
2. Structure of frond altogether cellular . . Dicranemeae. 
c. Tetrasporangia cruciately divided. Auxiliary 
cells situated in the interior region of the 
cortex, bearing a single recurved three-celled 
carpogonial branch and several lateral one- 
celled branches Rally menieae. 
Subfamily Gigartineae J. Agardh. 
There are two Australian genera, Iridophycus S. & G., a foliaceous form 
and Gigartina of various contours. In Iridophycus the cystocarps are 
immersed; in Gigartina they are at length prominent externally. 
IRIDOPHYCUS Setchell and Gardner. 
Syns. Iridea Bory, Iridaea J. Agardh. 
Thallus membranous-expanded, disc prostrate, below more or less shortly 
stipitate, stipe simple, expanded into an apophysis; apophysis smooth or 
verrucose, with one or more dichotomies, not bearing lateral processes, 
thallus expanded above, slightly membranous to cliartaceous ; usually 
irridescent under water; superficially smooth or more or less verrucose, 
