All around Athalmansvatn the ground was very hummocky, the mounds being from a foot to eighteen inches high, with narrow depressions or ruts between. The elevation of this region was about 2500 feet, and as the snow had only recently melted, everything was in consequence backward, Thalictrum and willows, etc., not yet being in flower.
Leaving Athalmansvatn a large tract of hummocky ground was crossed, covered chiefly by Cassiope hypnoides, Empetrum, Willows, Salix lanata and S. herbacea, Grey Lichens, such as Cladonia, and Mosses. After this our route lay across a piece of the northern desert land or Sandr, which is a barren, sandy, and stony expanse. The soil was a light brownish loam, and was easily blown about by the wind, and scattered all over it were large angular or rounded blocks of stone. Arabis petræa was the only plant occurring in any quantity over this region, and it formed a very conspicuous feature in the landscape, growing in rosettes closely adpressed to the soil with the racemes of flowers growing out horizontally.
As we travelled on in a southerly direction, Silene acaulis appeared and then a little thrift, Armeria sibirica, and the Arabis became less frequent. Here the soil was more sandy, and the strong wind blew clouds of dust. Still farther south, Armeria reigned supreme over the desert; but occasional patches containing Silene acaulis, Potentilla, Cerastium alpinum, and Silene maritima occurred. Where the soil became more loamy, Arabis petræa again came in. At the edge of the desert the willows were seen encroaching on the sand, and soon a willow and birch (Betula nana) scrub was passed through, which in its turn gave place to moister land with Empetrum, Pedicularis flammea, etc.
Near Blandá, Salir phyllicifolia was noticed for the first time. A good deal of hummocky ground was also passed over, and its characteristic and invariable features were noticed (v. later).
After passing over very rough morainic ground with snow still lying in patches and quite devoid of vegetation, we reached Hveravellir, a perfect oasis in the desert. The hot springs and fumaroles occur along a long line of fissure, and warm up the soil of a considerable tract of country in their neighbourhood. The effect on the vegetation is most striking, for a strip of verdant meadow-land occurs in the middle of bare country, covered in many places with snow at the end of June. All the flowers occurring there were in a very forward state, and a large number of different plants were obtained; some spots were yellow with buttercups, and the ground was carpeted with thyme in full bloom.
Botrychium lunaria occurred in quantity, and a very small variety of Ophioglossum vulgatum, O. vulgatum, var. polyphyllum, was found in a warm place. Selaginella spinosa was also abundant.
On the edges of this warm tract barren land occurred and in many places snow, so that there was a very sharp contrast between the warm and cold earth; and on the latter the willows were only just coming into leaf. This tract of country occurs at the edge of the great lava flow from Strytur.
Towards Strytur the lava was in places covered by "hummocky ground," which showed the usual features noticed elsewhere.
The characteristic plants seem invariably to be:—
*Carex vulgaris (rigida), a creeping variety.
*Salix lanata.
*Salix herbacea.
*Cassiope hypnoides.
*Empetrum nigrum (very abundant).
*Vaccinium uliginosum.
Loiseleuria procumbens.
Armeria sibirica.
Silene acaulis (not very frequent).
Bartsia alpina.
Pedicularis flammea.