19-5] Setchell-Gardner : Melanophyceae 615 



1. Agarum cribrosum Bory 

 Plate 63 



Holdfast consisting of numerous branched hapteres, slender and 

 diffuse in young specimens, thicker and more compact in older exposed 

 specimens ; stipe cylindrical, 3-30 cm. long, 5-8 mm. diam. ; blade 

 with median percurrent midrib 1.5-3 cm. wide, rather rigid, mem- 

 branaceous, plane, 5-9 dm. long, 2-5 dm. wide ; mature specimens 

 broadly ovate, cordate at base, margin smooth, unfolding at the base 

 from a scroll on either side of the midrib, profusely perforated ; per- 

 forations smooth, circular to very irregular in outline and up to 2 cm. 

 in diam. ; color dark brown, changing to olive green on drying ; sori 

 generally distributed over the blade. 



Growing on rocks in the sublittoral belt. Apparently very gen- 

 erally distributed from the Bering Sea to Sitka, Alaska, and recently 

 reported as far south as San Juan Island, Washington. 



Bory, in Diet, class., vol. 9, 1826, p. 193 (in part) ; Setchell, Kelps 

 of the U. S. and Alaska, 1912a, p. 155; Muenscher, Key to Phaeo- 

 phyceae, 1917, p. 260, fig. 12. 



Fucus crihrosus Mertens, in Linnaea, vol. 4, 1829, p. 52. Agarum 

 Gmelini Post, and Rupr., Illus. Alg., 1840, p. 11, pis. 20, 21; Saunders, 

 Alg. Harriman Exp., 1901, p. 430, pi. 61. Agarum Turneri Post, and 

 Rupr., Illus., 1840, p. 12, pi. 22 ; Saunders, Alg. Harriman Exp., 

 1901, p. 431. Agarum pertusum Post, and Rupr., Illus., 1840, p. 12, 

 pi, 23. Fucus Agarum Turner, Fuci, vol. 2, 1809, p. 10, pi. 75. 



The earliest name for this plant was Fucus Agarum Turner, but 

 since the generic name Agarum was limited by Postels and Ruprecht 

 to this and related species, this specific name became untenable and 

 they chose Turneri. By the laws of priority, however, the earlier 

 specific name crihrosum must be considered as the one to be adopted. 

 Postels and Ruprecht attempted to distinguish five species of which 

 three had broad flattened midribs and two had narrow prominent mid- 

 ribs, but our experience, which includes a study of a great variety of 

 Agarums from both the Atlantic and the Pacific coasts of North 

 America, leads us to feel that there is no distinct cleavage as to con- 

 stancy^ of broader or narrower midrib and as to coarser or finer per- 

 forations, all gradations appearing on both coasts. The unrolling of 

 the blade from two small cone-like scrolls distinguishes Agarum 

 crihrosum as a true Agarum. 



