FUCACE^ 233 



are a prolongation of those of which the thallus is composed, and 

 frequently project, through the mouth or ostiok of the conceptacle, into 

 the surrounding water. When infertile these hyphae are known as 

 paranemes or paraphyses. In the male conceptacles they are usually 

 branched, unbranched in the female. Both the barren and fertile con- 

 ceptacles are always first formed in the neighbourhood of the growing 

 point, the cavity originating from the absorption of a row of cells at 

 right angles to the surface. 



The antherids are produced on lateral branches of trie hyphae in the 

 male or in the upper part of bisexual conceptacles. Each consists of 

 an ovoid thin-walled or sometimes double-walled cell, the abundant 

 protoplasm of which breaks up into a number (usually sixty-four) of 



FIG. 209. Section of female conceptacle of F. vesiculosus, clothed with unbranched 

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



minute antherozoids, pointed at one end, with a pair of cilia of unequal 

 length placed laterally below the beak-like apex, and contains an orange- 

 red pigment spot and a nucleus. The olive-brown oogones are developed 

 from unbranched hyphae in the female, or in the lower part of bisexual 

 conceptacles. These fertile hyphae are at first unicellular, and are 

 bounded at the base by a septum ; the single cell subsequently divides 

 into a basal pedicel-cell, and an upper portion, which swells into a 

 spherical or ellipsoidal form, the oogone, filled with protoplasm coloured- 

 brown by phycophaein, and always provided with a wall composed of 

 two layers. Either the whole of the contents of the oogone contract 

 into a single oosphere, or it divides into two, four, or eight oospheres, 

 each with its own nucleus. Impregnation always takes place outside 



