620 University of California Puhlications in Botany [Vol.8 



elongating margins become secondary stipes, develop spirally and each 

 produces a secondary blade at its summit, the process perfecting dicho- 

 tomous branching; the secondary stipes become more or less decum- 

 bent and produce numerous hapteres along the lower margin ; the 

 blades produce fruit, disintegrate and bifurcate as before, the process 

 being repeated many times till a comj)lex organism is built up ; sori 

 unknown. 



Ruprecht, Bemerkungen, 1848, p. 67 (11). 



The type of the genus is A. kurilensis Rupr. from the island of 

 "Urup" in the Kurile group. At the same time that Ruprecht pro- 

 posed the genus he also proposed a second species, viz., A. radicans, 

 which is the Fucus bifidus of Gmelin (1768, p. 201, pi. 29, fig. 2) 

 which Ruprecht later 1851, p. 350) so recognized. The observations 

 on the development of ArthrotJiamnus by Yendo (1903) have thrown 

 much light on the systematic position of this previously little known 

 genus. It is obvious that it has close resemblances in development to 

 Thalassiopliyllum and Hedophyllum in the method of formation of 

 the secondary stipe and to the members of the sub-family Lessonieae 

 in the splitting of the transition region. Yendo 's later discussion 

 of Arthrothaninus (1914) is less clear than the earlier, but serves to 

 emphasize certain points. 



Arthrothamnus bifidus (Gmel.) J. Ag. 



Secondary or false stipes spirally twisted, marked with scars of 

 successive eroded blades, decumbent, attached by numerous hapteres, 

 ascending at the apices, developing into a scroll bearing the terminal 

 blades ; mucilage glands in the blades just beneath the cortex ; blade 

 membranaceous, linear, relatively long and acuminate. 



Aleutian Islands, Alaska. 



J. G. Agardh, De Lam., 1867, p. 28 ; Setchell and Gardner, Alg. 

 N. W. Amer., 1903, p. 267 ; Setchell, Kelps of the U. S. and Alaska, 

 1912a, p. 152. Arthrothamnus radicons Ruprecht, Algenst., 1848, 

 p. 68. Laminaria bifida Agardh, Sp., vol. 1, 1820, p. 122; Postels and 

 Ruprecht, Illus. Alg., 1840, p. 10, pi. 15. Fucus bifidus Gmelin, 

 Hist. Fuc, 1768, p. 201, pi. 29, fig. 2. 



We are including this rather singular species of algae in our 

 account on the authority of Areschoug (1884, part 5, p. 14), who 

 reports it from the Aleutian Islands. Being quite abundant just across 

 on the Asiatic coast, it may justly be expected to occur somewhere 

 among the islands of the Alaskan peninsula. 



