ON THE KAMIN ART ACEAE OF HOKKAIDO 
15 
6. Laminaria retigiosa Miyabe, sp. nov. 
(Plate 6) 
Japanese name. Hosome-kombu. 
Hosome (Matsumae), Bon-me (northern districts of Honshu), Iso- 
kombu (Shiribeshi), Hanaori-kombu (Matsumae). 
Holdfast composed of filamentous hapteres branching 6-7 times, 
of which the uppermost ones arise regularly in a whorl. Stipe 
smooth on surface, solid, more or less cylindrical at the base, 
slightly complanate above, of nearly the same diameter at both 
ends, 50-65 mm in diameter, ca. 5 cm in length. Blade entire, 
linear-lanceolate, reaching the maximum breadth at a distance of 
1/3 or 1/2 of the overall length of the blade from the base, round 
at the base ; in the individuals growing on littoral reefs, the blade 
is up to 0.7-2. 0 m, usually 1.3-1 .6m in length, and 5-12 cm, usually 
7-10 cm, in breadth, while in those growing in deep waters the 
length of the blade is nearly the same as in the former, but rarely 
attains to 3.5 m, and the breadth is 10-29 cm ; marginal portion 
thin, strongly undulate while young, becoming flat with the approach 
of maturity; median fascia 1/3 as wide as the entire breadth of 
the blade, 20mm in thickness; coriaceous in substance; rich in 
mucilage ; dark brown in color. Sporangial sori on both surfaces 
of the blade, covering nearly the whole surface in the lower part, 
becoming discontinuous in the upper portion, occurring chiefly on 
the median fascia. 
Mucilage ducts closely set in a single row in both stipe and 
blade, situated in the blade nearly at the middle portion between 
the medulla and the superficial cell layer. Medulla of the blade 
thin, consisting of filamentous cells mostly arranged in vertical 
rows. 
Habitat. Growing on rocky reefs between the lowest water 
mark and the depth of 5-6 fathoms. Distributed from Matsumae 
district as far north as Ishikari Bay, Shiribeshi Province. The 
so-called “Bon-me” occurring along the coasts of the Sanriku district 
and Iwaki Province in Honshu is probably identical with the present 
species. In Hokkaido this Laminaria is called “Hosome.” It is 
harvested there in early summer while the frond is not yet fully 
matured, and is exported to Uetsu districts of middle Honshu to 
meet the public demand at the Festival of Chügen or Bon. Hence 
