238 KJELLMAN, THE ALG OF THE ARCTIC SEA. 
being developed in the stipe, in consequence of which the surface of the stipe is as 
even and smooth as in L. digitata, and by the muciferous lacunw of the lamina being 
thinly scattered in the outermost part of the intermediate layer, small, and not surrounded 
with small cells of a peculiar shape, as is the case with the large lacunw in L. Clustoni 
situate near the middle layer. Thus L. nigripes in the shape, size, and position of the 
lacunw resembles L. digitata, more closely than L. Clustond. 
It is seen by the list of forms given above that the present Species is rather 
variable with regard to its habit and outward appearance. The external differences of 
different individuals are so great that it might be questioned whether there are not 
included several species in ZL. nigripes as here understood. Nevertheless, not having 
observed any constant difference in anatomical structure, I have thought best to regard 
the existing: differences as constituting different forms, not different species. 
It is fit that these differences phoma be set forth here. 
The rhizines (root-like fibers) issue in basifugal, alternate, rather regular whorls. 
They are sometimes long and fine, sometimes short and coarse. 
The stipe is always smooth, plable, black or blackish-brown when dried, never 
perceptibly thicker at the base than at the apex. It is sometimes of almost equal 
thickness, being then nearly terete, sometimes thicker at the top, being then more or 
less compressed upwards, even 23 cm. broad in its longest diameter. It is sometimes 
short, about an inch long, sometimes longer, attaining in larger specimens a length of 
2—®o feet. 
The lamina is of two different types. It is either reniform in outline, split to the 
base into much spreading segments, which are sometimes very numerous, repeatedly 
separated and 1—2 cm. broad, sometimes fewer, 3—4 cm. broad; or else it is broadly 
oblong and in this case sometimes entire, resembling the lamina of L. digitata f. wtegri- 
folia, sometimes split into a small number of broad, appressed segments, which are 
separated to the base of the lamina. Both these forms of lamina may be combined with 
short, almost terete, or long, more or less flattened stipe. In structure the lamina 
varies scarcely at all, the stipe is somewhat more variable, especially with regard to 
the muciferous lacune. In certain individuals these are very numerous, forming in 
transverse. section a dense, regular circle immediately beneath the cortical layer, in 
others they are fewer and at the same time larger, less regularly arranged and situate 
somewhat deeper in the intermediate layer of the stipe. 
The sorus is developed at the base of the lamina, where it forms a coherent girdle 
reaching quite or almost quite down to the lower margin of the lamina. In individuals 
that were in course of changing their lamina, | have seen the sorus expanded in the 
shape of bands in the zone between the old and the new lamina. 
Habitat. The present species occurs sublitoral, together with other Laminariacea, 
on rocky and stony bottom, at a depth of 5—15 fathoms. It lives both on exposed 
and on sheltered coasts. I have collected specimens in course of changing their lamina 
at Spitzbergen in July and September, specimens with zoosporangia in July (f. rend- 
formis), at the end of August, and in September and December (f. oblonga). In winter 
I found a Laminaria of the digitata group on the north coast of Spitzbergen furnished 
