222 KJELLMAN, THE ALGA OF THE ARCTIC SEA. 
Remark on the species. 1 have seen the Alaria the diagnosis of which I have given 
above, in a pretty considerable number of individuals younger as well as older, though 
none were very old. They had been collected at two points on the north coast of 
Siberia. The present species resembles the two preceding in the cauloid part and the 
costa, but differs from both of them in the shape of the lamina. This shape being 
constantly the same in older and younger specimens, I cannot but regard the plant as 
specifically distinct from both the preceding. The breadth of the lamina as compared 
with its length is considerably greater than in any of the species mentioned before, 
and the lamina is apparently always very thin. Even in specimens that are not more 
than 30 cm. long, the breadth is 10 cm. at the broadest part, immediately below the 
middle of the lamina. An incomplete specimen in my collections has the lamina 40 
cm. broad, thin as paper, and distinctly angular at the base. I do not know the 
approximate maximum of the length of the rhachis, not having found any older indi- 
vidual with the cauloid part preserved whole. The costa is somewhat less prominent 
than in the preceding species, but in other respects it is similar, though more often 
plane-convex. The sporophylls are pretty numerous; I have found even 20 developed 
at the same time in one individual. Although densely crowded, they are not so clus- 
tered as in A. dolichorhachis, and they are broader than in the last-named species and 
A. oblonga. Most of the specimens collected were sterile. In some the sporophylls 
were provided with developed sori occupying little more than the lower half of the 
sporophylls. The sterile part is very thin and wavy; the part bearing zoosporangia 1s 
also comparatively thin, almost membranaceous. Zoosporangia and paraphyses have 
the same shape and size as in the two preceding species. The length of the zoospo- 
rangia is 50—75 w., their thickness 10O—15 wu. 
Habitat. The present species is sublitoral and grows gregarious in 2—3 fathoms 
water on stony bottom on exposed coasts. In the month of July it was furnished with 
scarce zoosporangia on the north coast of Tshutsh-land. 
Geogr. Distrib. Known only from the Siberian Sea. 
Localities: the north coast of Tshutsh-land at Koljutshin Isle and at Pitlekay, 
the wintering station of the Vega expedition. 
Gen. Agarum (Bory.) Post. ct Rupr. 
Ill. Alg. p: 11; Bory. Dict. Class 9, p. 193; spec. excel. 
Agarum Turneri Post. et Rupr. 
Ill. Alg. p. 12. 
Descr. Agarum Turneri J. G. AG. Gronl. Lam. och Fue. p. 18. 
ig. » » Post. et Rupr. Fc. £. 22. 
Eesice. » » Fart. Anps. and Hat. Alg. Amer. N:o 12. 
Syn. Agarum Turneri J. G. Ac. 1. ¢.; Gronl. Alg. p. 110. 
» » Croat, Fl. Dise. p. 457. 
» » Dickin, Alg. Sutherl. 1, p. 141; Alg. Sutherl. 2, p. 191; Alg. Walker. p. 86; 
Alg. Cumberl. p. 237. 
Laminaria Agarum Lynas. Hydr. Dan. p. 24. 
