Rit (Vísindafélag Íslendinga) - 01.08.1930, Side 14

14
The valency of each species is determined according to its
degree of frequency in a certain number of square-units
(samples), which are chosen in the formation; each square-
unit is divided floristically, i. e. all the species growing in
this sample.
A circle is used to deiimit the square-units. The circle
delimiting the sample being tyio square metre in size. It is
thrown down at random in several places in each formation.
(For my investigation I chose 10). Each species gets ifs
marks according to, in how many of the square-units it is found.
The percentage is used to express the degree of frequency,
and thus a species which is found in all ten samples gets
the degree of frequency 100, another which is found in 9 is
awarded 90, etc.
Instead of the species themselves, one can put their life-
forms, and thus get the biological spectrum of the formation
which may be used for comparison when there are many
formations in question.
A FEW OF RAUNKIÆR’S LIFE-FORMS.
Ch. Chamaephyíes. They are plants which live above ground
during winter, but their bud-bearing stalks do not
reach 25 cm above the surface of the soil.
H. Hemicrypíophytes. Plants which preserve the buds in the
surface of the soil during winter.
G. Geophytes. Their buds remain far from, or near the
surface during winter.
HH. Hydrophytes or Helophytes.
Hydrophytes are perennial aquatic plants which
grow, either right under water, or a part of them
floats on the surface. Their buds sink to the bottom,
where they remain throughout the winter.
Helophytes are planfs growing in moisture, or in
soil saturated with water; but their stalks and leaves
reach above the water. The buds are under water in
winter, either in the bottom, or stuck in the mud.