ON THE I.AMINARIACEAE OF HOKKAIDO 
39 
what broadened midribs which become nearly twice as broad as 
the stipe. However, it may be natural to conclude that they should 
be referred to the present species rather than to A. Gmelini Mekt. 
from the fact that their perforations are smooth on the margins 
and spread all over the blade without any order. 
8. Tlialassiophyllum Post, et Rupr. 
Postels et Ruprecht, Illustrationes Algarum, p. 11, 1840. 
Holdfast is perennial, composed of filiform hapteres. Stipe 
gives rise to many branches, each of which bears a fan-shaped blade 
spirally scrolled. The outer part of a scroll is old whereas the 
inner part is young. Blade is destitute of any midrib, with 
numerous small perforations; the edge of the perforations are 
always torn and projecting on one surface ; mucilage canals and 
cryptostomata are absent. Sporangial sori are scattered on the 
blade surface forming irregular patches. 
Thalassiophyllum is a monotypic genus. 
Tlialassiophyllum Clathrus (Gmer.) Post, et Rupr. 
(Plate 28) 
Postels et Ruprecht, loc. cit., p. 11, Tab. XVIII-XIX, 1840. 
Illustration. GMELIN, Historia Fucorum, Tab. 33, 1768 ; POSTELS et RUPRECHT, 
loc. cit., Tab. XVIII-XIX, 1840. 
Japanese name. Kikuishi-kombu. 
Kikumeishi-kombu. 
Characters as described for the genus. Frond attaching to 
the rocks covered by water in flood-tide and exposed to the air in 
ebb-tide, standing upright or obliquely, from 33-66 cm up to 1.3- 
1.6 m in height, growing in remarkably dense clusters, which are 
said to look like bushes from afar when the tide is low. 
Habitat. Distributed from Etorofu Island, Kuriles, northward 
along the coasts of Kamtschatka, and from Alaska to California. 405 
40) The present species is now known to be distributed on one hand in the Kuriles 
from Uruppu, but not from Etorofu, northward (NAGAI, 1940, pp. 103-104), and on the 
other along the coast of North America as far south as the Straits of Juan de Fuca 
(Setchell and Gardner, 1925, p. 613), but not as far south as California as once 
mentioned by De TONI (1895, p. 336). 
