KONGL. SV. VET. AKADEMIENS HANDLINGAK. BAND 20. N:0 5. 175 



Of the form integerrima I have only seen a couple of specimens. Though I 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 Ruprecht, 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. pectinata 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. Judging 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 Pt. 

 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 endochronie, between which cells and the small cortical 

 cells rich in endochrome there lie 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 Pt. 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 elitoral. 

 I have usually found the former in 10 — :^0 fathoms water within the arctic region; but 

 it belongs to those Florideas 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 Kleen 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 



