. The botany of Iceland. Botany -- Iceland. PHYSICAL GEOGRAPHY 245 Owing to the variability of the wind-conditions, the dunes in the blown-sand districts are usually small and irregular in form; they are rarely higher than 3--4 metres, usually much less, and they are bound together by lyme grass and a few creeping dwarf willows. Sandy levels with low waves of sand are of general occurrence, and when moisture comes into play, the surface is cracked into numerous polygonal cakes by the action of desiccation or frost. The cracks are filled with drifted sand, so that the surface resembles a kind o
. The botany of Iceland. Botany -- Iceland. PHYSICAL GEOGRAPHY 245 Owing to the variability of the wind-conditions, the dunes in the blown-sand districts are usually small and irregular in form; they are rarely higher than 3--4 metres, usually much less, and they are bound together by lyme grass and a few creeping dwarf willows. Sandy levels with low waves of sand are of general occurrence, and when moisture comes into play, the surface is cracked into numerous polygonal cakes by the action of desiccation or frost. The cracks are filled with drifted sand, so that the surface resembles a kind of Fig. 16. Soil torn up by the wind. Large tracts in Landsvcit are occupied by these loess-like formations. Here several square miles of land, which were formerly wood-covered, are torn up by the north-east wind. The district of Landsveit, west of Hekla. (Phot. Th. Thoroddsen.) Ill tuff districts proper older and younger seolian formations are the thickest and most widely distributed, and often alternate with volcanic and glacial formations; but the tuff-dust is also car- ried to the basalt districts, where they initiate the formation of the loess-like layers known in Iceland as "; Smaller layers of "mohella" occur everywhere in valleys and lowlands alternating with older and more recent glacial formations, with peat and lava- streams, but they decrease in thickness the further they are away from the large stretches of blown sand in the tuff districts. "Mo- hella" usually resembles a fine, easily crumbled, yellowish-brown or grey tuff, which is often traversed by stems of plants and red tuff-tubes which have been formed around the decayed stems; they. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Kolderup Rosenvinge, L. (Lauritz), 1858-1939; Warming, Eugenius,
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