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 parl of the bottom is 
also quite without vegetation, even on stony bottom Algæ 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 Algæ, 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 Algæ were found, is the locality 
indicated with ©. 
It is important to distinguish between Algæ grown on the dredging locality 
and those found loose’. In some cases where such Algæ 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 Algæ 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’. 
1 C. H. OSTENFELD, Aalegræssets (Zostera marina’s) Væxtforhold 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. Jos. PETERSEN, “Kanonbaaden Hauchs Togter” 
where the signs indicating the Zostera, Laminaria and some other higher Algæ 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 Ascophyllum nodosum f. scorpioides; of others may 
also be mentioned: Phyllophora Brodiei, membranifolia and rubens, Ahnfellia plicata, Polysiphonia 
nigrescens and violacea, Cladostephus verticillatus, Halopteris filicina and scoparia, Sphacelaria cirrosa etc. 
