64 
THE SEAWEEDS 
Section Pteromorphae. 
Earlier fronds resembling trichotomous -pinnate leaves; later fronds 
above changed into spreading branches with much divided compound 
leaves, at first trichotomous then more vaguely dichotomous-pinnate, all the 
segments (laeiniae) filiform. Vesicles spherical, mutic. 
KEY TO THE SPECIES, 
a. Primary caul is compressed; rachides of the 
branches flattened below. Lower leaves con- 
spicuous and conjoined with the ala of the 
rachis. Upper leaves more or less tricho- 
tomous with filiform laeiniae. 
b. Lower leaves pinnatifid. Receptacles 
oblong 
bb. Lower leaves bipinnatifid. Receptacles 
lancoid 
aa. Primary caulis rounded; rachides of branches 
an gulat e-r ou nded. Lower leaves incon- 
spicuous with narrow segments. Upper 
leaves more or less trichotomous with fili- 
form laeiniae. "Vesicles large as a pea. 
c. Laeiniae of the leaves smooth 
cc. Laeiniae of the leaves warted (verruculose) 
from presence of cryptostomata. 
Vesicles very large and numerous . . 
S. varians Sonder. 
S. dedpiens- (R. Br.) 
J. Agardh. 
S. trichophyllum 
J. Agardh. 
S. verruculosum 
(Mert.) J. Agardh. 
Subgenus Arthrophycus J. Agardh. 
h rond consisting of an elongated branching axis bearing simple leaves 
without cryptostomata, vesicles crowned by a mucro or leaflet, and 
unarmed or dentate receptacles variously grouped. 
This subgenus is dominant in the southern parts of Australia and Tas- 
mania; two species are found in South Africa and one in New Zealand. 
There are 18 Australio-Tasmanian species, of which but three have so far 
been recorded from South Australia, but probably several of the others 
will be found here when the coast has been subjected to a more rigorous 
search. They are all conspicuous plants reaching a height of two, three, 
or more feet. 
In 1889 J G. Agardh published his magnificent Monograph on the Aus- 
tralian species of Sargassum. He himself instituted the majority of them. 
