232 



ALG^E 



of our coasts, Fucus vesiculosus (L.), and in other species of the genus. 

 In the 'gulfweed' of the 'Sargasso Sea' (Sargassum bacciferum, Ag.) 

 these bladders are spherical, and are elevated on pedicels above the 

 surface of the frond, giving them the appearance of berries (fig. 211). In 

 Halidrys (Grev.) they are ovoid, segmented, and pod-like in appearance 

 (fig. 206). 



The only reproductive organs of the Fucaceae are sexual, antherids 

 and oogones. Both kinds are formed in globular cavities known as con- 

 ceptacles, which are either distributed uniformly over the thallus, or are 

 congregated in particular portions of it, which are then known as re- 

 ceptacles. These are always either the terminal portions of branches, 

 or are in the parts provided with air-bladders, so as to be elevated above. 



.FiG. 208. Section of male conceptacle of F. vesicnlosus, clothed with branched 

 hyphae bearing the antherids ; o, ostiole (magnified). 



the surface of the water for the purpose of fertilisation. In Fucus (L.) 

 the receptacles constitute the warty extremities of the branches ; in 

 Himanthalia (Lyng.) the whole of the long whip-shaped stem which pro- 

 ceeds from the cup-shaped thallus is a receptacle (fig. 205) ; in Sargassum 

 (Ag.) they pccupy distinct fertile branches. In some species there are 

 separate male sundfema/e conceptacles, and then they are always dioecious ; 

 in other species antherids and oogones are contained in the same con- 

 ceptacle, the female organs occupying the lower, the male organs the 

 upper part of the cavity. There are also sometimes cavities of precisely 

 similar structure, but producing no sexual organs, which may be 

 degraded or aborted conceptacles. Both the fertile and barren con- 

 ceptacles are clothed internally by a dense weft of loose hyphae, which 



