The Botany of Iceland - 01.12.1930, Page 81

STUDIES ON THE VEGETATION OF ICKLAND
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pronounced southern (Th) types of plants it is one of the most re-
markable and interesting vegetations of Iceland.
The flag occurs as from 2—3 to 15—20 m. wide and often very
long clayey flats delimited upwards towards the mo by a more or
less connected slope and outwards towards the mýri by a con-
nected ridge (cf. figs. 11—12). The soil of the flag is level and hori-
zontal. If covered with water the whole of the summer it is a
naked clayey flat without any trace of knolls. If such a flat is laid
dry, the familiar polygonal cracks appear. If the soil is not covered
with water in the summer, it will always be cracked, and a grealer
or smaller number of small knolls covered with vegetation will be
spread over the surface. Such is the typical appearance of the flag.
If the soil grows drier still, the knolls increase in number as well
as in size and we get the flag mo, though the bare clay surface still
predominates.
The flag vegetation seems to comprise a number of for-
mations. Table 17 A shows the circling results for three such for-
mations, the Subularia flag, the Koenigia flag, and the flag mo.
The Subularia flag was examined in a single locality, the
mýri at Björk. Here a long strip of Koenigia flag occurred in con-
nection with a small brook. The Subularia flag was found at the
transition from the Koenigia flag to the brook. At the time when
the investigation was made, (the close ofJuly), the soil was covered
with water. In the deepest water only scattered specimens of Subn-
laria aquatica were found (table 17 A, 1), wliile further in (table
17 A, 2) it was found in company with some other species such as
Koenigia istandica, Juncus bufonius, Equisetum arvense.
From East Iceland a formation has been recorded by Helgi
Jónsson which must probably be referred to the flag. “Where
fhe soil has an admixture of clay little pools are formed in the
depressions which evaporate in the course of the summer. In these
places the vegetation varies not a little, consisting now almost ex-
clusively of Subularia aquatica, now on the other hand only of
Kanunculus reptans which colours such spots quite yellow. I have
seen both species occur in sucli quantities that they coloured the
whole bottom of the pool white or yellow. In other places I saw
that the vegetation consisted of Ranunculus reptans, Subularia aqua-
tica, Alopecurus fulvus and Juncus supinus fairly equally distributed,
so that neither one nor the other could be designated as the cha-
racteristic plant.”