1925] Setchellr-Gardner: Melanophyceae 619 



the blade dies away clear to the base, leaving; two separated, partial 

 blades, each at the extremity of a thickened basal margin which 

 resembles very closely a running rootstock; blade 60-75 cm. long, 

 segments very variable in width, somewhat rolled at the base, but not 

 auriculate; mucilage ducts present in both blade and stipe. 



Growing on rocks in exposed localities in the middle littoral belt. 

 Known in Bering. Sea and possibly extends for some distance south 

 along the coast of Alaska. 



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

 (Exsicc), no. XXVII, Notes on Algae, I, Zoe, 1901, p. 122; Setchell 

 and Gardner, Alg. N.W. Amer., 1903, p. 263, pi. 20 ; Saunders, Alg. 

 Harriman Exp., 1901, p. 430. Arthrothamnus Bongardicmus J. G. 

 Agardh, De Lam., 1867, p. 28 (in part). Hafgygia Bongardiana. f. 

 subsessilis Areschoug, Obs. Phyc, part 4, 1883, p. 5. 



This very curious plant has been described and illustrated by us 

 in our Algae of Northwestern America. It is intermediate between 

 the simpler decumbent Hedophyllum sessile and such a decumbent 

 species as Arthrothamnus bifidus (Gmel.) Ruprecht. Hedophyllum 

 spirale Yendo (1903) is an erect species, even more closely related to 

 the erect species of Arthrothamnus, difficult to place with precision. 

 Yendo 's later account (Notes on algae new to Japan II, 1914, 

 pp. 269-273, with fig.) seems to us to have confused several different 

 plants as well as distinctly different views on relationships. This is 

 particularly true as regards Postels and Ruprecht 's Laminaria Bon- 

 gardiana and is due. we think, to the fact that Yendo had access to 

 so little material for comparison. The plates of Postels and Ruprecht 

 (1840, pis. 13, 14) show clearly a digitate Laminaria, even plate 14 

 being quite possible of this interpretation. Very possibly plants of 

 Hedophyllum subsessile or of H. spirale were mixed in the material, 

 yet the conception of the species is largely that of a digitate Laminaria 

 and one that we have referred under L. platymeris. The Hedophyllum 

 subsessile of Setchell is very different from H. spirale of Yendo, the 

 latter approximating Arthrothamnus. 



48. Arthrothamnus Rupr. 



Original true stipe short, simple, flattened, attached by short stout 

 hapteres; original blade at first simple, smooth, flat, soon thickening 

 along the lower margin next to the stipe, and becoming more or less 

 cucullate; the two thickened margins become the meristems, the 

 original blade disintegrates to the top of the stipe, the thickening 



