74 SEAWEEDS 



among the adjacent cells. There is no division of 

 the original cell into pedicel-cell and sporangium. 

 When the sporangium reaches its full size the con- 

 tents are simultaneously divided into zoospores, which 

 do not wholly fill the interior. These escape by the 

 rupture of the wall at the apex, and their active 

 motion has been observed by Mr. R. M. Laing. 

 They are from 500 to 600 in number in each spor- 

 angium, and are of the same size as the antherozoids 

 of Fucaccce and the zoospores of the Laminariacccv, 

 which latter are formed in similar sporangia. The 

 number of sporangia in each conceptacle increases 

 with age, and they appear to crowd out, as it were, the 

 paraphyses, of which only a few are seen among the 

 sporangia at the base of a mature conceptacle. They 

 remain, however, in considerable numbers surround- 

 ing the mouth. The empty sporangia persist, unlike 

 the oogonia of the Fucaccce in a similar situation. 



This remarkable plant was included among the 

 FucacecK until it was placed apart in its present 

 position on its true nature being disclosed by the 

 admirable investigation of Miss Margaret Mitchell 

 and Miss Frances Whit ting. 1 Its nearest known 

 allies are undoubtedly the Laminariaeece, from 

 which it differs mainly in the sorus of sporangia 

 being enclosed within a conceptacle and thus definitely 

 limited, and by its remarkable apical cell. 



Its geographical range is in the southern ocean, 

 where it is found at the Cape of Good Hope, 

 Australia, New Zealand, Seal Island, &c. 



1 Murray's PhycologiccU Memoirs, part i. 1892, 



