184 OLAF GALL®E 
highlands, are either very poor in, or entirely devoid of, phanero- 
gams, and between the stones mosses (Grimmia hypnoides) chiefly 
occur, in part together with lichens; this will, however, be discussed 
more fully under the vegetation of the moss-carpets of the island. 
The Gravelly flats in the lowlands bear a scanty vegetation 
of herbs, (see e. g. Thoroddsen in vol. I, p. 326 of the present 
work; Jénsson’s lists are exhaustive, but, like Thoroddsen, he 
makes no mention of finding lichens). 
In river-gravel in the lowlands Chamenerium is common. The 
river-flats are occasionally inundated in spring, and are devoid of 
lichens. 
The gravelly flats of the plateau are “the parts of the rocky 
flat poorest in plants” (Jönsson). Here and there grow Luzula 
spicata, Oxyria digyna, Cerastium alpinum, Silene acaulis, Arabis 
petrea, Galium silvestre, Saxifraga cespitosa, etc. Moss-cushions 
(Dicranum falcatum) occur also, and, — as “collars” around larger 
stones, — small carpets of Grimmia hypnoides intermixed with lichens 
(Cetraria islandica and Cladonia) and phanerogams; this will be 
mentioned more fully under the moss-vegetation. The gravelly flats 
which I traversed just below the summit of the mountain “Sulur,” 
near Eyjafjördur, were still, on the 5th of July, supersaturated with 
the down-trickling snow-water, and were quite bare of vegetation. 
Sandy flats. Several kinds of sandy flats of various geological 
origin occur, partly in the lowlands, and partly in the highlands. 
Many of them are quite bare of plant-growth along such great tracts, 
that days intervene before a few individuals are again met with. 
The commoner types of sandy flats are: beach-sand (with a halo- 
philous herb-vegetation), which is devoid of lichens (owing to its 
contents of chloride of sodium); Jökul-sand (which is often inundated 
by Jökul-rivers) either devoid of, or with a very poor, herb-vegeta- 
tion, and without lichens (on account of inundations possibly fol- 
lowed by drifting sand); and lastly tracts of blown sand (Sander) 
of various origin, but more or less wind-affected on the surface by 
frequent and violent sand-storms. The different kinds of sand men- 
tioned here are devoid of lichens, owing to three essentially different 
reasons: (1) the occurrence of chloride of sodium in the soil (beach- 
sand), (2) frequent inundations (the sandy tracts below the Jökuls) 
or (3) drifting sand, (in the sandy tracts of the plateaux and else- 
where). 
I traversed, in several places, such extensive sandy tracts, as 
