STUDIES ON THE VEGETATION OF ICELAND 713 
prineipally or exclusively find such species as Koenigia islandica, 
Sedum villosum, Juncus bufonius, biglumis and triglumis, Triglochin 
palustre, Equisetum arvense, Cerastium cœæspitosum, Sagina nodosa, 
Minuartia verna. On the small knolls the vegetation is connected 
and here we find the species Agrostis alba, Deschampsia alpina, the 
Festuca spp., Armeria vulgaris, Rumex acetosa and several others, 
principally such as are common to mo and jathar. 
Helgi Jönsson was the first to describe the flag vegetation, 
though without thus naming it. His description of the vegetation on 
the “clayey flats” which is referred to the “open vegetation of the low- 
lands” corresponds to the description given above of the flag vege- 
tation. In “Studier over Ost Islands Vegetation” 1895, p. 86, he says, 
“they (i. e. the clayey flats) have most frequently a monotonous ve- 
getation consisting of Sedum villosum, Koenigia islandica, Juncus 
triglumis and other more casually growing plants. This vegetation 
on clay varies not a little in composition; of the forms I have seen, 
I note especially the following: a. The vegetation consists only of 
Sedum villosum which occurs in a rather dense growth and gives a 
fresh appearance to the clayey flats by its pretty flowers. b. The 
vegetation consists only of Koenigia islandica which also occurs in 
a rather dense growth but in this locality it is most frequently of 
a red colour. c. The vegetation consists of Sedum villosum and 
Koenigia islandica either in equal quantities or with now one, now 
the other as the dominant. d. The vegetation consists of Juncus 
triglumis as the dominant plant, besides scattered individuals of 
Sedum villosum and Koenigia islandica, and Agrostis alba in scat- 
tered tufts.” 
“It should be noted that in many places a transition to the mo 
vegetation is seen where most of the species of the mo occur 
(Gramineae, Juncaceae) growing in scattered tufts with bare clay 
between, it is merely a younger stage of the grass mo.” 
In “Vegetationen paa Snæfellsnæs” 1900, pp. 43—44, we read: 
“Plants characteristic of the clayey flats are Sedum villosum, Koenigia 
islandica, Juncus alpinus and J. triglumis. The two first-mentioned 
are most prominent and often occur in an astonishing quantity. 
The most frequently occurring species are Agrostis alba, Aira alpina, 
Sagina nodosa, Triglochin palustre, Epilobium palustre, Luzula spi- 
cata, L. multiflora. In East Iceland this vegetation had quite the 
same appearance. When these flats dry up in the summer, they 
are often divided by cracks into many small polygonal areas, 
