56 M. FOSLIE. [1905 



on the northern coast of Norway in places where the species grows 

 in company with the said species. Here it frequently encompasses 

 small pebbles, and develops a rather feeble crust with coarse 

 branches, 2 — 3 mm. thick, sparely divided, subdistant or approxi- 

 mate, sometimes, peculiarly when the alga is attacked by animals, 

 fairly coalescing towards the centre. It is often wholly accrete 

 with small specimens of L. glaciale, or one species partly en- 

 compasses the other so as to make it almost impossible to draw 

 the line between them. In this form I have found the sporangia 

 two-parted and four- parted, mentioned above, in the same specimen. 

 I never saw the form so diverging, when growing alone, and it 

 is not improbable that the specimens in question should be looked 

 upon as a hybrid. I have seen young specimens from Iceland of 

 a form similarly diverging. Also from Scotland (Port Bannatyne) 

 there are a couple of specimens which resemble this form, and 

 which are likely to be referred to L. tophiforme. They occurred 

 together with L. glaciale, encompassing small pebbles, developing 

 a feeble crust and branches like those of the specimens from nor- 

 thern Norway mentioned above. But on the other hand they are 

 considerably approaching certain forms of L. glaciale. 



The form divergens includes L. divergens in Norw. Lithoth. 

 As is stated 1. c, I have not earlier found conceptacles fully deve- 

 loped. But in looking over the material anew, I found bisporic 

 sporangia. It is a delicate form, hardly distinguishable form L. 

 Granii, though the branches are mostly more elongated than in 

 the latter. It also includes a coarser form, which is in habit re- 

 sembling a coarse L. soriferum f. squarrosa. Also f. divergens 

 is generally freely developed on the bottom. Sometimes, however, 

 it is attached to hard objects and will develop a crust which, 

 though feeble, is fairly extended. Such specimens are hardly 

 distinguishable from a Lithoth. glaciale feebly developed, and parti- 

 cularly from L. Granii. 



With some doubt I consider f. flabellata as belonging to this 

 species. The type specimen, as a matter of fact, shows a crust 

 faintly developed and comparatively long branches, as in attached 

 specimens of f. divergens. Therefore, I now refer it to the spe- 



