76 H. MØLHOLM HANSEN 
lozenges, the surface contracting so much owing to the disappear- 
ance of the water that it cracks. On the flats here. described these 
are of very different duration, most frequently they last a very short 
time, disappearing when the surface becomes damp again. For the 
vegetation these cracks, as far as I can see, are of no importance, 
since it nearly always occurs on the lozenges themselves.” 
In "Vegetationen paa Syd Island”, 1905, pp. 13—14, he writes, 
“Open clayey flats are met with in many places.” “The vegetation 
on the clayey flats is always very poor in species, and only where 
the vegetation of the clayey flats is passing into the surrounding 
associations do we meet with a greater abundance of species. The 
typical clayey flats as a rule contain the same species everywhere. 
The few species which are exclusively or principally found on the 
clayey flats and must thus be designated as characteristic of them 
are the following: Sedum villosum, Koenigia islandica, Spergula ar- 
vensis, Juncus alpinus, J. triglumis. The most commonly occurring 
are Agrostis alba, Juncus bufonius, Equiselum arvense, Epilobium pa- 
lustre, Poa annua, Stellaria crassifolia, St. media, Ceraslium vulgare, 
Polygonum aviculare, Sagina procumbens. More rarely we meet with 
Triglochin palustre, Alopecurus fulvus, Scirpus pauciflorus, Eriophorum 
Scheuchzeri, Sedum annuum, Poa glauca, Rumex acetosa, Silene ma- 
ritima, Phleum alpinum, Myosotis arvensis, Veronica serpyllifolia, 
Rumex acetosella, Thymus serpyllum, Leontodon.” 
By the above quotations from H. Jönsson’s descriptions of the 
vegetation and by the circling results given here the flag vegetation 
has been characterised floristically. If we are to characterise the 
vegetation biologically, the best way will be to compare the bio- 
logical spectra of the flag and the neighbouring vegetations, i.e. the 
mo and the jadar. Table 18 gives the biological spectra of these 
types of vegetation at Björk and Lakjamöt, viz. respectively moist 
mo, flag (or flag mo), jadar (or myri). 
It will appear from the table that the flag vegetation is poorer 
in species and shows less density of species than the surrounding 
types of vegetation, the mo and the jadar. This applies especially 
to the Koenigia flag. As regards the content of Raunkier’s life 
forms, the flag is especially remarkable by its high Th percentage. 
As shown above, the Subularia flag had a Th percentage of 71, the 
Koenigia flag a Th percentage of 20.9, and the flag mo a Th per- 
centage of 9.4. The table likewise shows a comparatively high H 
percentage and comparatively low Ch and G percentages. The pro- 
