tildels kan skyldes Indskrumpning ved Tørringen. Dette Fund 

 tyder paa, at C. mucronatum er en Art, som er i Færd med at 

 udvide sit Udbredelsesomraade ved Europas Kyster, og dette 

 støtter igen den Antagelse, at den ikke er oprindelig hjemme- 

 hørende ved Europa men er blevet indført dertil fra sit exotiske 

 Voxeomraade, selv om det maa være sket for længere Tid siden, 

 eftersom Arten allerede i 1839 er blevet fundet ved Irlands Kyst 

 ifølge Cotton (1. c. p. 116). I Limfjorden mener Østersdykkerne, 

 efter hvad Mag. Spärck meddeler mig, at have iagttaget den i 

 flere Aar, og det er, efter dens nuværende Udbredelse at dømme, 

 rimeligt nok, at det maa flere Aar, siden den indvandrede i denne 

 Fjord; men paa den anden Side kan det ikke tænkes, at den 

 kan have levet der i mange Aar, da den i saa Fald ikke kunde 

 have undgaaet Naturhistorikernes Opmærksomhed. 



On some Marine Algæ recently introduced into Danish 



waters. 



By 



L. Kolderup Rosenvinge. 



(Abstract). 



1. Gigartina mamillosa(G.&W.) J. Ag., which had formerly never been 

 found on the Danish coasts, was discovered in 1869 by I. P. Jacobsen at Thi- 

 sted in the Limfjord, where it was found growing on the moles of the harbour 

 and the adjacent stony slopes of the harbour; I found it at the same place 

 in 1890 and 1893 growing abundantly and well developed, a little above 

 low- water mark, but it has never been found at other places in the Limfjord, 

 although this water has been rather well investigated. It is evident that 

 this species cannot have existed at Thisted before 1825, as the isthmus 

 separating the fjord from the North Sea was in that year broken through, 

 and the salinity of the water in that part of the fjord was until then ex- 

 tremely slight. As the Thisted part (Bredning) of the Limfjord is connected 

 with the other parts of the fjord only by narrow channels with exclusively 

 Zostera vegetation, and as the species in question does not occur in other 

 parts of the fjord, it must therefore have been carried to Thisted by a ves- 

 sel on which it was growing. The salinity in the western part of the Lim- 

 fjord is now 29 p. m. 



The same species was found in 1911 or 1912 on a stony slope north 

 of the harbour of Aarhus by Mr. V. Petersson, and I found it in the same 

 place in 1915. It grew here rather abundantly, but the specimens were 

 smaller than at Thisted, evidently owing to the lesser salinity of the water. 



