PHAOPHYCEA 5d 
currents, &c., play a very important part in producing 
mere growth forms which abound in common species 
like F. vesiculosus. 
Geographical Distribution —The Fucacee occur in all 
seas, those of the north temperate and arctic regions 
differing considerably from those of the south tem- 
perate and antarctic. Each possesses peculiar types, 
while the intervening tropical zone has also its charac- 
teristic genera. The south temperate zone is richer 
in generic types than any other region, while the 
tropical zone (especially the south sub-tropical) with 
comparatively few genera furnishes the most species. 
Among the southern temperate generic types with 
few species there are Durvillea, Sarcophycus, Myrio- 
desma, Carpoglossum, Hormosira, Marginaria, Scyto- 
thalia, Carpophyllum, Landsburghia, Xiphophora, and 
Phyllospora. Of small genera represented in both 
northern and southern temperate zones there are 
only Pycnophycus and Halidrys. The peculiarly 
northern genera are Himanthalia, Ascophyllum, 
Pelvetia, LEgregia, Coccophora, and Fucus. (Ff. 
vesiculosus has been recorded from the Cape 
and Australia, but the record is open to 
question.) Cystophora has a remarkable distribu- 
tion, its twenty or more species being limited to 
warm Australian seas. Sargasswm, which reaches its 
maximum in the same region, contains about 150 
species, but of a more distinctly tropical character 
than Cystophora. Cystophyllum has ten species, 
mostly sub-tropical, while Cystoseira, with thirty 
species, has a wider range into temperate seas. 
Turbinaria, with a few species, is strictly tropical. 
