42 



Tromsø Museums Aarshefter. 14. 1891. 



gated or somewhat irregular frond, with the branchsystems 

 often issuing only upwards, spreading, longer and more or 

 less eurved branches, and more seldom anastomosing below. 

 Both forms seem to be commonly dispersed along the north- 

 em coast of Norway, at several places abundant. 



Last summer I found L. alcicorne Kjellm. between 

 Tromso and Grindo in scattered individuals. Here it grows 

 in company with L. soriferum f. divaricata, and it passes so 

 gradually into this form that it is impossible to draw any 

 limit. Cp. pl. 3, fig, 4. Stromfelt also met with a spe- 

 eimen of L. soriferum at Iceland showing a transition to L. 

 alcicorne. Cp. S t r o m f. Isl. Algveg. p. 18. I therefore re- 

 gard it a form of L. soriferum. Typical speeimens of this 

 form are very scarce at Tromso, the only place where it is 

 hitherto found. 



Lithothamnion norvegicum Aresch. (Kjellm.) 



N. Iah. AlgfiL p. 122; L. calcareum var. norvegicum Arescli. Obs. 

 Phyc. 3, p. 4—5. 



f. globulata nob. 



f. spliærica vel Kubsphærica, ramis e centro solido vel axi prima- 

 rio undiquo egredientibus, fastigiatis, inferne interdum plus minus coali- 

 tis. Tab 3 f fig. 7. 



f. distans nob. 



f. globoso-elongata, ramis divaricatis, plus minus elongatis. Fig. 

 Kjellm. 1. c. t. 5, fig. 9—10. 



This species is nearly related to L. soriferum, but it is 



* 



a smaller and more delicate plant. However, the northern 

 form found in Nordland is coarser than the southern one, 

 and the form which I have collected at Skorpen in the nor- 

 thern part of Tromso amt is still coarser. The species pos- 

 sesses forms similar with L. soriferum, the above quoted f. 

 globatula and f. distans is analogous respectively to L. sori- 

 ferum f. globosa and f. divaricata. I found both the named 

 forms at Skorpen on a depth of 3 — 5 fathoms jointly with 





