OF SOUTH AUSTRALIA. 
49 
They are cut off from the utricle by a plug of cellulose-like substance. 
When ripe, the content of the gametangium breaks up into biciliate gametes 
of two sizes. The smaller are supposed to be male, and the larger female 
gametes. Conjugation between them has not been observed, but the larger 
gametes have been seen to develop into young thalli. The genus is of 
world-wide distribution. 
Fig. 29. — Diagrammatic sections of different forms of G odium : (a) cross section 
of Adherent form; (b) cross section of Spherical form; (c) cross 
section of Dichotomous form; (d) longitudinal section of Dichotomous 
10 m. x, mte-iOT or infe ior laye ; y, cxte.ior or upper palisade 
laye:. (Suggested by O. C. Schmidt.) 
V 
KEY TO THE SPECIES, 
a. Fronds unbranched. 
b. Thallus black-green, applanate C. Luccisii. 
bb. Thallus light-green, spongiform . . . . C. spongiosum. 
bbb. Thallus globular C. pomoides and 
C. mamillosum. 
aa. Fronds dichotomous. 
c. Thallus cylindrical C. Muelleri , 
C. galeatum , and 
C. fragile. 
cc. Thallus flattened especially beneath 
the forkings C. decorticatum. 
