572 University of California Publications in Botany [Vol.8 



Agardh, Syn. Alg. Scand., 1817, p. xii and p. 12, Urn. mid.; 

 Greville, Alg. Brit., 1830, p. 44. 



The name Chordaria was first proposed by Link in 1809 to include 



a series of different plants, none of which, however, belong to this 



entity as now constituted. C. Agardh (1817, p. xii) modified the 



limits of the genus to include C. rotunda, C. divaricata, C. flagelli- 



formis, C. cabrera, and C. Filum and three other doubtful species. Of 



these C. flagelliformis is the only northern species of the series now 



generally included under the genus, but some authors also include 



C. divaricata. Greville (1830, p. 44, pi. 7) was the first definitely to 



establish the present limits of the genus by pointing out a type, viz., 



C. flagelliformis. 



Key to the Species 



1. Fronds flagelliform, cylindrical throughout 2 



1. Fronds irregular in diameter, flattened at the branching ...3. C. dissessa (p. 574) 

 2. Fronds relatively robust, up to 9 dm. high, usually with many long, 



slender, primary branches 1. C. flagelliformis (p. 572) 



2. Fronds slender, up to 3.5 dm. high, primary branches patent, scattered 

 along the whole main axis up to 4 cm. long 2. C. gracilis (p. 573) 



1. Chordaria flagelliformis (Muell.) Ag. 



Fronds attached by a small disk, solitary or in groups, lubricous, 

 solid, 2-5 dm. (up to 9 dm.) long, branching close to the base into 

 many branches of nearly equal length, or the main axis percurrent 

 giving rise to numerous alternate branches, shorter above ; branches 

 usually of 3 orders; peripheral assimilating filaments 6-8 cells long, 

 with terminal cell nearly spherical, and with numerous hyaline hairs 

 interspersed ; color dark olive brown, nearly black ; zoosporangia ovoid 

 to pyriform, arising at the base of the cortical filaments. 



Growing on rocks in the upper sublittoral belt. 



Agardh, Syn. Alg. Scand., 1817, p. 12 and p. xii, Fucus flagelli- 

 formis Mueller, Flor. Dan., 1771, pi. 650, 



This species in its various forms seems to be exclusively boreal, 

 though extending much farther south on the Atlantic shore than on 

 the Pacific shore of North America. It is very common on the 

 American and European shores of the North Atlantic. It has been 

 reported as far north as the Spitzbergen Islands and in the Baltic 

 Sea. The following forms have been reported within our territory. 



