248 



ALG.^ 



attached in tufts to larger algae, and resembling in habit the fresh-water 

 Confervaceag. The thallus consists of segmented more or less branched 

 filaments, either composed of a single row of cells or corticated. The 

 growing point of the filament does not lie at its apex, but at the extremity 

 of a basal portion, the true thallus, the terminal hair-like portion being 



deciduous. The zoosporanges are of 

 both kinds, and are either external 

 and stalked, or are ordinary cells 

 of a filament, whether terminal or 

 intercalary. Multilocular sporanges 

 are sometmies produced on the 





' ^M\ 1/v 



Fig. 221. — Ectocarpus invcstiens Hauck, 

 epiphytic on Gracila7-ia comptessa 

 ( X 250). (After Burnet.) 



Fig. '22-2. — Conjugation of zoogametes of 

 pLctocarptis siliculosits Ktz. /, a~f, female 

 zoogamete, gr^idually losing its cilia. //, 

 male zoogametes swarming round female zoo- 

 gamete ///, a-e, stages in the coalescence 

 of the male and female zoogametes ( x 790). 

 (After Berthold.) 



same individual as the unilocular, but at a later period. The swarm- 

 cells which escape from the unilocular sporanges are non-sexual zoospores, 

 germinating directly after coming to rest, and investing themselves with 

 a cell-wall. Those contained in the multilocular sporanges all escape 

 through a single terminal opening, and partake to a certain extent of 

 sexual properties, or become under certain conditions zoogametes. 



