103 



Relation to other species. This plant in some respects corre- 

 sponds with the northern L. varians, the form Harveyi nearly 

 connected in habit with certain forms of that species, but it is in 

 fact most nearly allied to L. polymorphum, and sterile specimens 

 especially of f. depressa easily may be confounded with the latter. 

 The colour, however, is frequently lighter and more fugitivel, the 

 marginal portion in. general comparatively thicker and, so far as I 

 have seen, never concentric zonated, nor that of new-formed crusts 

 overlapping extraneous objects, and the surface appears not to be 

 furnished with concentric or radiating striae, as often is the case 

 particularly in younger individuals of L. polymorphum, although 

 not always. Fertile specimens are on the other hand easily di- 

 stinguished, and it cannot then be confounded with any form of 

 the latter. 



Habitat With us it apparently grows in the upper part of 

 the sublitoral region. It appears to prefer protected places. Spe- 

 cimens collected in the former half of August were provided with 

 partly emptied partly not fully developed conceptacles of sporangia. 

 On the coast of Britain it bears the named organs as well as 

 conceptacles of cystocarps in August, and on the coast of France 

 in April, September and November, • in most cases with not mature 

 sporangia and carpospores, but also emptied conceptacles. 



Occurrence. Only found at Mandal (Wille), apparently scarce 

 (f. depressa and transitions to f. Harveyi), and two not quite cer- 

 tain specimens of f. Harveyi at Sulen in Sogn (Bo ye). 



Geogr. Distribution. Britain (Harvey, Batters); the Atlantic 

 coast of France (Crouan, Le Jolis, Bornet); the Mediterranean 

 Sea 'Philippi, Solms-Laubach) ; the Adriatic Sea (Ktitzing, 

 Hauck). 



Lithothamnion compactum Kjellm. 



N. Ish. Algfl. p. 132 (101). 

 Descr. et Fig. Lithothamnion compactum Kjellm. 1. c. et t. 6., fig. 8—12. 

 Fig. „ „ tab. nostr. 19. fig. 1 — 1. 



Syn. Lithothamnion polymorphum Farl. New Engl. Alg. p. 182 ; saltern ex parte. 

 „ „ Kjellm. Algenv. Murm. Meer. p. 8. 



v circumscriptum R validum Rosenv. Grenl. Havalg. p. 775. 



