136 SEAWEEDS 



reproduction, however, the parts are reversed, since 

 none is known in Bryopsis and Codium. 



Went, 1 however, in studying Codium tomentosum, 

 found both kinds of zoosporangia on the same 

 individual plants. Sometimes the small gametes do 

 not appear until after the dispersal of the larger 

 ones and they may be formed from the same basal 

 cell. He never observed any union of the two sorts, 

 and successfully cultivated the contents of the larger 

 kind of gametangia or sporangia. But it is im- 

 possible to say in this case whether there had been 

 conjugation or not. 



In Derlesia we have only non-sexual reproduction, 

 and, if the genus be rightly placed here, this fact 

 also may have its significance, since Derbesia in other 

 respects strongly resembles Vaucheriacecc. The 

 zoosporangia arise as lateral outgrowths from the 

 filaments, and contain 8 20 zoospores with a fringe 

 of cilia on the anterior end. As mentioned under 

 Vaucheriacece the nuclei in the parent cell become 

 reduced by union to the number of zoospores formed. 

 However, it is plainly an aberrant type, and needs 

 further investigation. 



The Geographical Distribution. Bryopsis occurs in 

 all seas, but more abundantly in warmer waters. 

 Codium also has an extensive range in the warm and 

 temperate seas of the world. Derbesia belongs to the 

 north temperate and tropical Atlantic (both Euro- 

 pean and American), and occurs also on the Australian 

 coasts. All three genera are British, and (with 

 Vaucheria and Halicystis) constitute our represent- 

 1 Vergrad. d. Ned. Botan. Vereeniging, 1889. 



