ur 
KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 20. N:0 5. 17 
Of the form integerrima I have only seen a couple of specimens. Though | have no 
reason to suppose it to be any very constant or independent form, I have wished to 
call attention to it, because, as has already been pointed out by Ruprecur, it shows a 
remarkable approximation to Pt. asplenioides and, on this account, might possibly be 
considered as a proof of phylogenetic connection between this species and Pt. pectinata. 
It differs from typical Pt. pectinuta by its almost complete want of so-called rami com- 
positi and by more spreading, generally perfectly entire rami foliiformes, which makes 
it very dissimilar to typical Pt. pectinata. dudging from some few cases observed, 
the sporocarps issue generally from the outer side of the leaf-shaped branches, sitting 
on distinct, unarticulated stalks, sometimes from the middle of the rhachis itself. 
The pretty form litoralis I have met with on the north coast of Norway among 
Pt. elegans, which it resembles rather much on a cursory examination. As is shown 
by the figure given, it differs most considerably from typical Pt. pectinata; however, 
from its agreeing essentially with this species in structure and ramification, I suppose 
it to be a variety of it produced by different conditions of life. It differs from /?. 
pectinata by being somewhat, though only slightly, tufted and by its smallness, slender- 
ness and far denser branching. How considerable the difference of thickness is between 
f. litoralis and the typical form, is seen on comparing the figures-4 and 6 in tab. 15, 
which exhibit transverse sections of corresponding portions of the thallus of these two 
forms. These figures moreover show that there exists a certain difference in structure 
between these forms. In the typical Pt. pectinata the central cell of the transverse 
section in the fullgrown branches of the last order but one, is surrounded with a complete 
circle of large cells poor in endochrome, between which cells and the small cortical 
cells rich in endochrome there le other smaller cells poor in endochrome. The structure 
of f. litoralis differs from this in so far that the central cell adjoins large cells poor in 
endochrome only in the direction of the longest axis of the transverse cut, whereas 
along the short axis it is immediately contiguous to small cells rich in endochrome. 
In consequence of this, in a fullgrown axis of the last order but one in a Pt. pectinata 
f. litoralis the row of axial cells along the middle of the axis is translucent, which is 
not the case in typical /t. pectinata. A comparison of fig. 4 with fig. 5 shows the 
structure of older and younger portions of the frond in the former to differ rather 
much. It is to be seen also in the latter figure that the row of axial cells is not sur- 
rounded with a complete circle of large cells poor in endochrome, even in the older 
parts of the branches. Only sterile individuals are known. 
Habitat. The typical form and f. integerrima are decidedly sublitoral or clitoral. 
I have usually found the former in 10—20 fathoms water within the arctic region; but 
it belongs to those Floridexe which descend to the greatest depths. On the coast of 
Spitzbergen I have dredged specimens in one place from a depth of 150 fathoms, in 
two other places at 80—100 fathoms. According to Kieren it is a deep-water form 
at Nordlanden. I have met with it at Finmarken on exposed shores at a depth of 15 
—20 fathoms, in the interior of Altenfjord in 5—6 fathoms water. In the White Sea 
it occurs at pretty varying depths, from one and a half to 10 fathoms. In the eastern 
part of the Murman Sea it is generally found at 10—20 fathoms. It thrives on bottoms 
