PHMOSPORE^ 



247 



spores contained in the multilocular sporanges, which must therefore 

 be regarded as zoogametes, and the phenomena are the same as in 

 the Ectocarpacese. Areschoug (' Observ. Phycol., iii., 1875) describes 

 a remarkable kind of conjugation — altogether peculiar as far as the 

 brown seaweeds are concerned — in the swarm-spores of Dictyosiphon 

 hippuroides (Lyng.), somewhat resembling that in the Conjugatae. Two, 

 or sometimes three, of the zoogametes cohere by their apices, and the 

 contents slowly pass entirely into one of them, but only after they have 

 come to rest. Both then become invested with a thin coat of cellulose, 

 and the one into which the endochrome has passed, which may be called 

 the female element, subsequently germinates. In other cases the con- 

 jugating zoogametes put out conjugating tubes not unlike those of the 

 Zygnemacese. Some of the zoospores also germinate without conju- 

 gating. 



LrrERATURE. 

 Reinke — Pringsheim's Jahrb. wiss. Uot. , 1878, p. 362. 



The Mesoglceace/e or ChordariaceEe (Myrionema, Grev., Leathesia, 

 Gray, Chordaria, Ag., Mesogloea, Ag., 

 &c.) are seaweeds with a gelatinous 

 or cartilaginous thallus of hemisphe- 

 rical or cylindrical outline, variable in 

 size, and forming small gelatinous or 

 slimy cushions or branching tufts on 

 larger seaweeds. Each filament is com- 

 posed of a vertical central row of cells, 

 surrounded by a ' cortex ' of radial rows 

 at right angles to the central row. On 

 these cortical rows are placed the zoo- 

 sporanges, which are both unilocular 

 and multilocular, concealed within the 

 periphery of the 'frond.' Nothing is 

 known of the conjugation of the 

 swarm-spores; they appear to germi- 

 nate directly, giving rise to a creep- 

 ing branched filament, from which the ascending axes subsequently rise. 



Fig. 220. — Chordaria flagelliforfnis Ag. 

 Transverse section through thallus, with 

 unilocular zoosporanges (x 200). (After 

 Kiitzing.) 



The EcTOCARPACE^ constitute an ill-defined group of small, occa- 

 sionally microscopic, marine (Elachista, Duby, Ectocarpus, Lyng., 

 Giraudia, Derb.) or rarely fresh-water (Pleurocladia, Br.) Algse, usually 



