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on the British coasts ; Sphacella in the Mediter- 

 ranean ; Phloiocaulon, Anisocladus, and Ptilopogon in 

 the Southern Ocean. Sphacelaria is represented in 

 all seas. 



CHORISTOCARPACE.E. 



General Characters. The thallus is filamentous, 

 consisting of a single row of cells, and possesses an 

 apical cell by which it grows in length. The repro- 

 ductive organs, both unilocular and plurilocular spor- 

 angia, arise as lateral outgrowths of the filaments, 

 as do also the vegetative gemmae. 



The Thallus is in all cases filamentous and 

 branched never of more than one cell-row. The 

 apical cell produces all the cells i.e., there is no 

 intercalary growth whatever. 



The Reproductive Organs. The plurilocular sporan- 

 gia of Discosporangium form a remarkable rectangular 

 plate one layer thick, arising laterally from a slight 

 outward bulging of the wall of one of the cells of the 

 thallus. The loculi open outwards. In Chwisto- 

 carpus the corresponding bodies more nearly approach 

 those of Ectocarpacece. In Pleurocladia (a fresh-water 

 form placed here) the plurilocular sporangia also 

 resemble those of Ectocarpacece, and this genus further 

 possesses unilocular sporangia (not known in Disco- 

 sporangium and Choristocarpus) of similar type. 



The gemmae are known only in Choristocarpus and 

 are lateral outgrowths of two, rarely three, cells, the 

 upper being the larger. After they are shed the 



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