23 
K. MIYAKE 
3. Arthrothamnus Ruprecht 
Ruprecht, Bemerkungen, p. 67, 1848. 
To this genus belong two species : one, Arthrothamnus bifidus, is 
distributed from Kushiro northeastwards along the coasts of the 
Kuriles and Kamtschatka as far as Behring Island, and the other, 
A. kurilensis, is known only from the Kuriles north of Etorofu Island. 
The blade, in both species, is linear in shape, and comes with the 
approach of maturity to produce an aurieuiate outgrowth on both 
sides of its base. The overwintered old blade is shed in spring 
leaving a scar extending from the broadened top of the stipe to 
the base of each outgrowth. The aurieuiate outgrowth develops 
into a new stipe and blade.' J7) In A. bifidus, the stipe is flattened 
and gives rise along both its sides to hapteres which keep the 
decumbent thallus firmly attached to the rocks. A. kurilensis is 
characterized by having an erect, but never repent, thallus. In 
both species, the age of the thallus can easily be ascertained from 
the number of ramifications of the stipe. 
1. Arthrothamnus bifidus (Gmel.) Ruhr. 
(Plate 18) 
Ruprecht, Bemerkungen, p. 68, 1848. 
Syn. Fucus bifidus Gmelin, Hist. Fuc., p. 201, pi. 29, fig. 2, 1768. 
Illustration. Gmelin, Ioc. cit., pi. 29, fig. 2, 1768; Postels et Ruprecht, Illus- 
trationes Algarum. Tab. XV. 1840. 
■Japanese name. Nekoashi-kombu. 
Mimi-kombu, Shita-kombu. 
Matured frond attaching to the rocks by means of filiform 
hapteres formed along both sides of the complanate stipe. Blade 
1.3-5.0m in length, 4. 3-6. 5 cm in width, somewhat broadened toward 
the base; base rounded and with no outgrowth while young, but 
provided with aurieuiate outgrowths when matured; median fascia 
a shallow depression, as thick as the marginal portions; coriaceous 
in substance. 
Specimens collected in June 1893 at Shinshiru Island, Kuriles, 
are found to have on one surface of the blade two rows of spo- 
rangial sori. 
27) Cf. Yamada, 1934, in Jour. Jap. Bot., 10 (11) : 732 -736, figs. 1-2 ; Idem., 1935, 
ibid., 11 (5) : 318-320, figs. 1-6 ; Tokida, in Trans. Sapp. Nat. Hist. Soe., 15 (2) : 60-66, 
figs. 1-5. 
