19-5] SetclicU-Gardner : MeJanophyceae 427 



distinctly discoid chromatophores and the opposite arrangement of 

 most of the main branches clearly distinguish this species from any 

 other on onr coast. 



17. Ectocarpus Parksii S. and G. 

 Plate 49, fig. 15 



Fronds 5-7 cm. high, densely caespitose, flaccid ; main filaments of 

 erect fronds, 34— 40/^ diam. in the lower part, tapering very gradually 

 upward, profusely and alternateh' branched, very slightly corticated 

 at the base ; branches of succeeding orders reduced in diameter, long 

 and tapering very gradually upward, not terminating in hairs; 

 ultimate ramuli lO-lS/x diam., terminal cell 5-7/>i diam. ; cells cylin- 

 drical to very slightly doliiform, 40-70/a long in the main filaments, 

 quadrate to subquadrate above; chromatophores numerous, irregular 

 plates densely crowded together and more or less connected in the 

 ramuli, becoming more regularly disk-shaped and separate in the 

 lower parts of the main filaments ; gametangia relatively sparse, sessile, 

 straight or slightly curved upward, mostly on the subterminal and 

 terminal ramuli, secund, 4-10 in a group, occasionally solitary, blunt 

 fusiform to subconical, 35-45/x, long, 18-22/i, broad. 



Growing on Gracilaria confervoides (L.) Grev. in a small cove, 

 San Francisco Bay, northeast of Tiburon, Marin County, California. 



Setchell and Gardner, Phyc. Cont. VII, 1924, p. 1. 



This species of Ectocarpus appears to be a very short lived spring 

 form. Within a month after it was first observed, apparently just 

 coming into fruit, it had largely disappeared. Its structure seems to 

 relate it to several of our west coast species. Its long, slender, grad- 

 ually tapering filaments, profusely branched, are similar to those of 

 E. siliculosus (Dillw.) Lyngb. Its sessile gametangia are similar in 

 form to those of E. Taoniae S. and G. The secund arrangement of the 

 gametangia and the disk-shaped chromatophores are characters belong- 

 ing to E. gramdosoides S. and G. The delicate fronds, with profuse, 

 alternate branching, the disk-shaped chromatophores, and the groups 

 of small, sessile, blunt, secund gametangia make a combination of 

 characters not found in any other species. 



