96 
THE SEAWEEDS 
the stem grows obliquely to the surface, where its leaves are buoyed by 
their vesicles, and it often stretches ' horizontally along the waves for many 
fathoms. 
The southern coast of Australia, especially in the east, Tasmania. 
Widely distributed in the colder waters of the Pacific, California to Cape 
Horn 
Fig. 53. — Macrocystis pyrifera — (a) terminal primary segment, splitting 
into lateral leaves; (b) lateral adult leaf with float. 
Family SPOROCHNACEAE. 
The most elegant members of the Brown Seaweeds, with a filiform thallus 
of considerable size, diversity and beauty of form. The lower part of the 
frond is parenchymatous, but the upper cells in rows free from one another. 
The reproductive organs occur in clusters (sori) as obovate or ellipsoid 
unilocular sporangia, borne on slender branching filaments. 
