The Botany of Iceland - 01.12.1930, Blaðsíða 138

128
H. M0LIIOI.M HANSEN
As previously mentioned, the flag vegetation is peculiar to this
level, and this type of vegetation lias just those characteristics which
were pointed out for Zone IV, or the jaðar vegetation, viz. a low
chamaephyte percentage and high H and Th percentages; these
conditions are, however, more pronounced in the flag than in the
jaðar vegetation. Thus the forces which produce and sustain the
flag vegetation act, though in slighter degree, wherever this level of
moisture occurs, even where no flag is developed.
The cryptophytes, i. e. the helopliytes and geophytes, are
peculiar to the lower sections of the scale of moisture, just as Ch,
Th, and H are peculiar to its upper sections. HH are most abun-
dant in the lowlands and the south country, decreasing in quantity
as we pass to higher levels. This agrees witli the HH percentage
in tlie Greenlandish local floras where, as previously shown, the
HH percentage decreases from south to north along the west coast
as well as the east coast.
As regards the distribution of HH in the scale of moisturc,
they naturally occur in the greatest quantity in the flói on soil that
is constantly covered with water; thence they decrease strongly
through the mýri, until they disappear entirely in jaðar.
The geophytes have a similar distribution. In Zone VII,
the dampest section of the scale, they attain their maximum; thence
the G percentage decreases strongly and steadily throughout the scale
until, in Zone I, they attain their minimum wliich is lowest in the
north country and highland tracts, highest in the south country.
Thus the geophytes, on this point too, present a contrast to the
therophytes and chamaephytes.
In regard to species the cryptophytes show the same conformity
to law; thus the freshwater vegetation of Vestflrðir has an HH
percentage of 70, the mýri vegetation an HH percentage of only 9.
In the same locality the G percentage of the mýri is 25, of the mo,
14, and of melar only 9.
We have now seen the distribution of Raunkiær’s life-forms
in the Icelandic scale of moisture. From the circling results it
appears that the individual life-forms attain their maximum deve-
lopment at different grades of the scale. Passing from the bottom
to the top of the scale, the following sequence appears
Heloph. —> Geoph. —> Hemicryptoph. —* Theroph. & Chamaeph.