1925] Setchell-Gardner: Melanophyceae 709 



1. Cystoseira osmundacea (Menz.) Ag. 



Fronds robust, perennial, up to 6 m. long; stipe nearly triangular 

 in cross-section, somewhat geniculate, having numerous prominent 

 scars caused by the disintegration of the primary branches; flattened 

 portion in the lower part of the primary branches with deep rounded 

 sinuses and jjrominent pinnae, rounded at the outer ends, very closely 

 resembling the fronds of certain ferns, gradually reduced in size 

 toward the outer end of the rhachis and finally merging into the long, 

 branched, filiform branches ; vesicles 5-12 seriate, 4-6 mm. diam., 

 mostly in the branches having only the receptacular ramuli beyond; 

 receptacles conspicuous, abundant, often much branched, terminating 

 the ramuli; plants dioecious. 



Growing in tide pools in the lower littoral belt and in the upper 

 sublittoral belt, usually in moderately sheltered localities. 



Central Oregon (Coos Bay) to Lower California (Ensenada). 



Agardh, Sp. I, 1820, p. 69 ; Gardner, New Fucaceae, 1913, p. 333. 

 Fucus osmundaoeus Menzies, in Turner, Hist. Fuc, vol. 2, 1809, p. 92, 

 pi. 105. 



The type locality of the species is Port Trinidad, Humboldt County, 

 California. Two forms, fairly constant in structure, have been noted 

 as follows : 



Cystoseira osmundacea f. tjrpica Gardner 



This form comprises the shorter specimens, more robust throughout, 

 usually with fewer (5-8) vesicles in a series. It grows, as a rule, in 

 more exposed localities in tide pools along low-tide level, and seems to 

 be limited largely to the central and northern parts of the range. 



Gardner, New Fucaceae, 1913, p. 335, pis. 51, 52. 



Cystoseira osmundacea f. expansa (Ag.) Setchell 



Forma expansa includes the more delicate and slender, much 

 elongated (up to 6 m. long) specimens with smaller vesicles and a 

 larger number (7-12) in a series. It is most luxuriant in the southern 

 part of the range. 



Setchell. in Collins, Holden and Setchell, Phyc. Bor.-Amer. 

 (Exsicc), no. XLVIII ; Gardner, New Fucaceae, 1913, p. 336, pi. 53. 

 Cystoseira expansa Agardh, Syst. Alg., 1824, p. 290. Cystoseira 

 osmundacea Collins, Holden and Setchell, loc. cit., nos. XCVI and 

 CXV a, not h. Both distributions are small parts of plants. 



