98 KJELLMAN, THE ALG OF THE ARCTIC SEA. 
nearly that of L. soriferum and the species resembling it. It differs from ZL. glaciale, 
besides in structure, even by the lesser thickness and more cylindrical shape of the 
processes and by its tetrasporic sporangia. With ZL. soriferwm or L. Ungeri it cannot 
be confounded, the habit being different and the sporangia becoming grown over. » The 
name is meant to denote that in character it stands between ZL. glaciale and L. sori- 
ferum and the species most closely allied to the latter. 
Habitat. The specimens I have collected myself, were taken in 5—10 fathoms 
water on stony bottom, in a pretty well-sheltered locality. Here scattered individuals 
were found. On the coast of Norway it has ripe tetrasporangia in the month of June. 
Geogr. Distr. It is known hitherto only from the ‘Atlantic region of the Polar 
Sea. The most northerly locality where it has been found, is Karlsé at Lat. N. 70°. 
Localities: The Norwegian Polar Sea: Tromsé amt, for inst. at Tromsé (Fosrip) 
and Karlsé; Finmarken, at Vads6 (Fostig). 
Lithothamnion flavescens nob. 
L. fronde crustacea, arcte adnata; crusta tenuiore, vix 1 mm. crassa, e roseo flavescente, scabriuscula, 
limbo levi, subnitido, obsolete concentrice striato, margine subundulato, e cellulis majoribus formata; concepta- 
culis sporocarpiferis et sporangiferis in eodem specimine sparsis, illis depresso-conicis, apice perforatis, his demum 
innatis, creberrimis, magnis, diametro 700 w. hemispheericis, prominentibus; sporangiis quaternas sporas foventibus, 
sporis maturis, 190— 220 w. longis, 50—100 «w. crassis. Tab. 6, fig. 1—7. 
Description of the species. Habit. The plant forms incrustations on other Litho- 
thamnia, for inst. Z. glaciale, LZ. compactum, and on shells of Balanidw. The crust is 
closely adherent to the substratum, thin, scarcely one mm. thick, always uneven 
when older, finely rugged and squamellate on the greater part of its surface. The 
greater or smaller unevenness of the surface is caused by the substratum, to which it 
clings closely. However the brim is smooth, feebly shining, with few indistinct con- 
centric stripes; the edge is uneven, shallowly undulating. When younger the crust has 
a faint rosy colour, which passes afterwards into faint brownish-yellow, which colour 
increases when the plant dies, and appears particularly strong in the fracture (fig. 1). 
Structure of the frond. The lower co-axil system is feebly developed, its anticli- 
nals converge gradually toward the matrix. In fragments of the frond, which have a 
thickness of 0,3 mim., it takes up about 25 uw. The cells are elongated, about twice as 
long as broad, rectangular or rhomboidical in radial section (fig. 3—4). In the upper 
thickening-layer of the frond the cells, on a radial section, are four-angular, squarish 
or rectangular, their longitudinal axis in the latter case running sometimes in the di- 
rection of the radius, sometimes in that of the tangent. The outermost cells in par- 
ticular are in the latter position. Their thickness amounts to 10—13 «.; their length 
does not exceed 15 u. The cell-rooms are rounded, the walls about 2,5 w. thick. The 
surface cells are nearly isodiametrical in tangential direction, with rounded or rounded- 
angular cell-rooms, 5—8 «“. in diameter; the thickness of the dissepiment amounts to 
4—5 uw. (fig. 5). 
