574 University of California Publications in Botany [^'ou 8 



at wide angles with the primary branches ; color light brown ; zoo- 

 sporangia unknown ; cortical filaments short, composed of 2-3 cells 

 with a subspherical terminal cell. 



Growing in abundance on stones. West shore of Amaknak Island, 

 Unalaska, Alaska. 



Setchell and Gardner, Phyc. Cont., 1924, p. 8. 



The slender percurrent axis bearing numerous short, almost equal, 

 lateral branches over most of its length with short branchlets and all 

 axes patent to one another, give the plants of the single collection 

 available a very distinctive appearance. The plants are young and 

 sterile, but the structure of the frond, the terminal subapical growth 

 and the discoid holdfast indicate its affinities with Chordaria. In the 

 Algae of Northwest America (1903, p. 248) we placed this plant 

 under Dictyosiphon foenicidaceivs (Huds.) Grev., an untenable posi- 

 tion, since the subterminal growth and other details of structure plainly 

 show its different nature. 



3. Chordaria dissessa S. and G. 



Plate 41, fig. 57, and plate 75 



Fronds attached by a small disk, 15-25 cm. high, up to 2 mm. thick, 

 moderately and alternately branched, usually wider at the branching, 

 but swollen in some parts and contracted in others, older parts at 

 times fistulous, olive brown in color, composed of a medulla of longi- 

 tudinal filaments giving rise to a cortex of short assimilating filaments ; 

 filaments of the medulla composed of large, colorless, closely compact, 

 thick-walled cells up to 120/^ diam. in the central part of the frond, 

 many times longer than the diameter, becoming much shorter and 

 narrower toward the periphery ; cortical erect filaments cylindrical, 

 simple or branched, not closely compact, 4-6/x diam., composed of 2-4 

 cells, terminal cell swollen and globular ; hairs unknown ; branches of 

 each different order reduced in size, terminal ramuli long-attenuate 

 and acute, angles mostly wide and rounded ; zoosporangia obovoid to 

 ellipsoidal, 36-42/^ long, 28-32jli broad ; gametangia unknown. 



Growing on eel grass in the middle and lower littoral belts. East 

 Sound, Orcas Island, Washington. 



Setchell and Gardner, Phyc. Cont., 1924, p. 8. Castagnea divari- 

 cata Setchell and Gardner, Alg. N.W. Amer., 1903, p. 249 (not C. 

 divaricata (Ag.) J. Ag.). 



The resemblance between Chordaria dissessa and C. divaricata 

 (Ag.) Grev. is superficially close, but the former has its main axes less 



