21 



part of the bottom in the Danish waters is not overgrown , especially in the more 

 open waters. This is especially the case with regard to the North Sea, which is 

 quite without vegetation except at some few places in the most northern part of 

 the region referred to here. In the Skagerak the greater pari of the bottom is 

 also quite without vegetation, even on stony bottom Algse are often lacking. Here 

 and there some small overgrown plots are however found, but it is only at some 

 few places that a more abundant vegetation is found, especially near the land, e. g. 

 at Hirshals and Bragerne. Also in the other waters large tracts are without vege- 

 tation, especially the soft bottom, which in the Kattegat and the Baltic extends over 

 wide areas in the greater depths. 



A main rule is, that the total quantity of the vegetation is generally the greater 

 the more sheltered the place is. It must however be remembered, that in the 

 more sheltered waters we have the Zostera, which grows on sand bottom or on 

 mud bottom more or less mixed with sand', while the algal vegetation is found 

 on stony bottom. The last applies not only to bottom exclusively or predominantly 

 consisting of stones but also to sand bottom or soft bottom with scattered stones. 

 On the last mentioned kind of bottom there is commonly, according to the con- 

 ditions, scattered algal vegetation or Zostera vegetation with Algae, which is indi- 

 cated on the charts by a special sign. But also on true stony bottom scattered 

 algal vegetation is often found especially in deeper water. In such cases the lo- 

 cality is however indicated on the charts with the same sign as those with unin- 

 terrupted algal vegetation. Only when the vegetation is practically lacking, but 

 where however some few scattered specimens of Algse were found, is the locality 

 indicated with ©. 



It is important to distinguish between Algse grown on the dredging locality 

 and those found loose ^. In some cases where such Algse occur they have been 

 brought by chance from another locality, in other cases they appear in large 

 quantities and always at the same place, where they keep living for a long time. 

 Such collections of loose Algse are found e. g. at some places near Anholt and 

 near Moen ; they are given a special sign. Of a different nature is a number of 

 more or less transformed loose forms of different algal species connected with the 

 Zostera vegetation; probably they have been carried into this vegetation after having 

 been torn loose, but when there have been kept among the Zostera plants and have 

 gone on living perhaps for a long time, propagating by division, while reproduction 

 by spores has ceased and the appearance has become more or less transformed"'. 



' C. H O.STENFELI), Aalegrsessets (Zoslera maiina's) Vjextforhold og Udbredelse i vore Farvande. 

 Beretn. fra den danske biologiske Station. XVI. 1908. (Report from the Danish Biological Station. XVI.) 



Such a distinction has not been made in C. G. Johs. Petersen, "Kanonbaaden Hauchs Togter" 

 where the signs indicating the Zostera, Lnminaria and some other higher Alga; in the Kattegat are 

 given on the Atlas, Plate III (1893). In some single cases at any rate, plants are here noted as growing 

 at localities, where according to my experience the bottom is quite without vegetation. 



' The largest and perhaps the best known is AscoplujUiim nodosum f. scorpioides; of others may 

 also be mentioned: Pliylloplwia Broduei, membianifoUa and ruhens, Ahnfellia pUcala, Polijsiplionia 

 niyi cscens and violacca, Cladostepluis verticillatus, HalopLevis /ilicina and scoparia, Sphacelmiu cirrosa etc. 



