FUCALES (HETEROGENERATAE) 191 



there is copious branching which results in bilateral, radial and 

 bilaterally radial thalli. 



(5) Anomalae, composed of two genera, Hormosira and Notheiuy 

 both confined to the Antipodes. Growth is brought about by a 

 group of cells instead of a single cell. 



DURVILLEACEAE 



Durvillea (after I. D. D'Urville). Fig. 128. 



The sporophyte is a dark olive brown or black in colour and 

 possesses very much the appearance of a Laminaria. The large 



Fig. 128. Durvillea antarctica. A, young plant ( x ^). B, adult plant (much 

 reduced). C, stipe and holdfast ( x ^). (After Herriot.) 



solid stipe arises from a scutate holdfast and very soon passes into a 

 flat, expanded, fan-shaped lamina, which later becomes split into 

 segments although no definite appendages are produced from this 

 frond. The ends of the older laminae become frayed and broken off 

 by wave action, whilst the holdfast may attain a diameter of 2 ft. 

 through the addition of new tissue annually. If this secondary 

 growth did not occur the plant would soon be torn from its moor- 

 ings because the holdfast is continually becoming riddled with 

 holes through the boring operations of molluscs. The macro- and 

 microsporangia, which are borne in conceptacles on different plants 



