ROCKWEEDS AND GULFWEEDS (FUCALES) 



321 



The gametes are produced in a multicellular structure known 

 as a gametangium, and, as in case of a sporangium, the gametan- 

 gium may be formed from a cell within the filament or from a 

 terminal cell on a short lateral branch. The small cubical cells 

 composing a gametangium are packed closely together and each 



FIG. 276. Portions of two fila- 

 ments of Ectocarpus, showing repro- 

 duction. At s are shown spo- 

 rangia, and between the filaments, 

 a zoospore. At g are shown a game- 

 tangium and a single sperm and two 

 sperms fusing at the right . Redrawn 

 with modifications from Curtis. 



FIG. 277. Plant body of 

 Fucus vesiculosus (X ). In 

 the swollen tips are the con- 

 ceptacles in which the sex 

 organs occur, and at various 

 places occur bladder - like 

 floats. 



produces a biciliate zoospore-like gamete. After escaping the 

 gametes fuse in pairs and form zygospores. In this plant such 

 gradations occur between sporangia and gametangia and between 

 zoospores and gametes, as to afford considerable support for the 

 theory that gametes are simply zoospores which are too small 

 to function alone. 



Rockweeds and Gulf weeds (Fucales). In this order the 

 plant body may reach a meter in length, but is usually much 



