46 M. FOSLIE. [1905- 



or dimorpha whose central parts are dissolved by boring mussels. 

 When forming small bundles, it will also approach f. tuberculata 

 of the species mentioned. 



The conceptacles of sporangia on one side approach those of 

 L. fornicatum so as to make it difficult to draw any limit in this 

 respect. On the other hand, they come near to those of L. sori- 

 ferutn, and also here a limit is scarcely to be drawn, although 

 they are often less prominent than fully developed ones in the 

 said species. The roof, which is traversed by about 50 muciferous 

 canals, usually falls to decay, leaving a cupshaped scar, which is 

 gradually effaced by new- formed tissue. However, overgrown 

 conceptacles now and then occur in the peripherical portion of 

 a branch. 



I have thought it questionable whether L. TJngeri together 

 with L. noclulosum, admitted below, should not be considered as 

 a form of L. norvegicum, as they belong to the same series of 

 forms. But 1 have afterwards found this less probable, although 

 a definite line can hardly be drawn. In the limitation here taken,, 

 it also approaches other species. Thus I have above mentioned 

 that it will approach L. fornicatum, and particularly coarse, sterile 

 specimens seem to be hardly distinguishable from L. grancle. On 

 the other hand, coarse specimens of f. flexuosa will so nearly 

 approach L. soriferum f. squarrosa that it is difficult to draw the 

 line. It is distinguished from the latter mainly by its branches 

 generally more curved. Specimens of this form with more delicate 

 branches very nearly approach L. noclulosum. This is the case 

 e. g. with the form of the species occurring on the coast of Ice- 

 land. I refer this form to f. flexuosa, though it is more delicate 

 than usual. I have seen specimens well developed from Bildudalur, 

 about 10 cm. in diameter. 1 ) 



This species occurs in a depth of 3 — 15 fathoms and prefers 

 places sheltered, where the tidals are running strongly. In such 

 places it appears, as a general rule, in shallow water, often forming 

 considerable banks, while in places somewhat exposed it descends 



a ) In this form from Iceland I found four-parted as well as two-parted spor- 

 angia, the latter, however, in small number, but apparently ripe. 



