238 KJELLMAN, THE ALG.E 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 lacunaj 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 lacunas in L. Clustoni 

 situate near the middle layer. Thus L. nigripes in the shape, size, and position of the 

 lacunas resembles L. digitata more closely than L. Clustoni. 



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 L. yiigripes 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 should 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, pliable, 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 2^ cm. broad in its longest diameter. It is sometimes 

 short, about an inch long, sometimes longer, attaining in larger specimens a length of 

 2—3 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, teserabling the lamina of L. digitata f. ivtegri- 

 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 lacunas. 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, 1 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 Laminariacece, 

 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. reni- 

 formis), at the end of August, and in September and December (f. oblonga). In winter 

 I found a Laviinaria of the digitata group on the north coast of Spitzbergen furnished 



