1925] Setchell-Gardner: Melanophycecu 487 



though they are more frequently to be found on the pedicels up to 

 fifteen cells long:. At times sessile forms are to be found on the erect 

 filaments about two-thirds of the way up to the apex, but more gen- 

 erally they are terminal on small lateral ramuli on the ereet filaments 

 arising from the middle to near the apices. Rarely there are small 

 lateral forms on the ramuli. Finally, they may rarely be terminal or 

 intercalary and seriate on the erect filaments although the erect fila- 

 ments are usually piliferous. The terminal forms on pedicels, and 

 particularly those on the main erect filaments, are often quite blunt, 

 even elavate. Others on the prostrate filaments are narrow and 

 sharply attenuated, at times terminated by a sterile pointed filament, 

 in effect intercalary. Many of the gametangia, terminal on the ramuli, 

 are composed of a single series of loculi. Most of the others are two 

 or more seriate. The hair filaments do not seem to be abundant. They 

 arise laterally on the main filaments, usually above the center. The 

 meristem in these hairs is at the base which is surrounded by a sheath 

 similar to that described by Sauvageau (1898, p. 47) for MyrUmema. 

 The ramuli are decidedly curved upwards. The species is similar to 

 Myrionema speciosum from the Faeroes, described by Borgesen (1902, 

 p. 421). Our plant is more slender in all of its parts, has much longer 

 gametaiigia. and possesses, in addition to the sessile, secund gametangia 

 figured by Borgesen, occasional intercalary ones and many terminal 

 ones on the numerous clustered ramuli. These ramuli are in turn 

 occasionally branched, usually arise in groups, sometimes whorled, two 

 or three arising from the same cell, in other instances they are secund. 

 The species often grows in association with other members of the 

 Myrionemataceae and the Ectocarpaceae. As a rule, the main erect 

 filaments do not enter into the formation of gametangia, but give rise 

 either to sessile gametangia or to the ramuli. No zoospores have been 

 observed in the so-called zoosporangia. We suspect that these may 

 represent pathological conditions. 



18. Compsonema immixtum S. and G. 



Thallus inconspicuous, the basal filaments creeping among the 

 gametangia of the host ; erect filaments very numerous, all bearing 

 gametangia ; hairs and zoosporangia unknown ; gametangia narrowly 

 ellipsoidal, 24-30/t long. 



Growing on Colpomerria sinuosa f. deformans. Isla Partida, Gulf 

 of California. 



