604 University of California Publications in Botany [Vol. 8 



order. In the family Laminariaceae, the only suspected annuals of 

 our coast are Costarht costata, Cymathaere triplieata and Agarum 

 fimbria turn. The annual character and the discoid holdfast clearly 

 distinguish this species. 



9. Laminaria dentigera Kjellm. 



Holdfast composed of a dense mass of rigid hapteres; stipe 30-35 

 cm. long, smooth, flexuose, thickest at the base, slightly attenuated 

 upward, somewhat compressed at the apex, mucilage ducts large, 

 densely crowded in a circle just beneath the surface ; blade sub- 

 lanceolate, simple cuneate at the base, thick, smooth, dark brown or 

 almost black, shining, dissected nearly to the base with narrow or 

 wide linear lobes with lacerated margins. 



Growing in the sublittoral belt. Aleutian Islands to the Bering 

 Strait. 



Kjellman, Om Beringh. Algfl., 1889, p. 45, pi. 2, figs. 10-14; 

 Setchell, Kelps of U. S. and Alaska, 1912a, p. 151. Laminaria denti- 

 gera f. brevipes Setchell and Gardner, Alg. N.W. Amer., 1903, p. 259. 



Laminaria dentigera, while seemingly distinct in appearance from 

 any of the truly digitate species, is somewhat difficult to diagnose with 

 certainty. The rather stout, nearly cylindrical, or often more or less 

 compressed, stipe, the sharply cuneate base of the blade and the 

 usually numerous and narrow segments of the blade with lacerate 

 margins as if irregularly dentate, distinguish the typical plants. As 

 is frequent among the Laminariaceae, there are long-stiped and short- 

 stiped forms with other variations tending to obscure the limits of the 

 species. The form, previously described by us as var. brevipes 

 (Setchell and Gardner, 1903, p. 259) is probably close to Kjellman 's 

 type while var. longipes S. and G. (loc. cit.) is in our present opinion, 

 to be separated on account of its decidedly flattened stipe. We now 

 refer the latter to L. platymeris de la Pyl. In spite of these, however, 

 Laminaria dentigera seems clearly distinct from the forms usually 

 reckoned under L. Bongardiana P. and R. (L. platymeris De la Pyl.) 

 with the normal form of which, according to Kjellman, Areschoug 

 confused it. It is to be distinguished from L. Andersowii Farlow in 

 having the circle of mucilage glands of the stipe situated among the 

 outer tissues. The type of L. dentigera came from Bering Island, on 

 the Asiatic side of the Bering Sea. 





