146 
THE SEAWEEDS 
Order GIGARTININAE. 
CONSPECTUS OF THE SUBFAMILIES. 
Acrotylaceae. 
The gonimoblast, the bundle of fertilized filaments which bear the carpo- 
spores, closely conjoined with the surrounding tissues, leaving as it were 
a cavity clothed within by a membrane. Tetrasporangia zonately divided. 
Gigartinaceae. 
Gonimoblast consisting of a bundle (caespitulum) of branches passing 
into and conjoined with the surrounding tissues, evolving the carpospores 
within the complex. Tetrasporangia mostly cruciately divided. 
Rhodophyllidaoeae. 
Gonimoblast divided into several lobes, from auxiliary cells radiating 
inwards in all directions. Carpospores acrogenous. Tetrasporangia 
zonately divided. 
Family ACROTYLACEAE Schmitz. 
ACROTYLUS J. Agardh. 
Frond compressed, linear, dichotomous; composed of three strata of cells, 
the medullary of branching, reticulately-anastomosing slender filaments ; the 
intermediate of roundish-angular cells; the cortical of seriated, coloured 
Fig. 20 . — Acrotylus australis : a, plant; b, portion 
of branch with conceptacles ; c, 
section through the frond and a con- 
ceptacle; d, section through a sorus; 
e, tetraspore. (After Harvey.) 
