'IRAQ AND THE PERSIAN GULF' [‎133v] (271/862)

mm
184 CLIMATE, VEGETATION, AND FAUNA
the Irano-Turanian region extending southwards, and the Saharo-
Sindian region spreading northwards from the deserts of Arabia.
Many plants are bi-regional, but a large proportion are mono-regional
and can be regarded as indicator species. The date-palm, for example,
although a cultivated plant of oases, is restricted to Saharo-Sindian
territory, and in Iraq ceases to be an economic factor north of the
35th parallel. Similarly, the mugweed, Artemisia Herba-alba, is re
stricted to Irano-Turanian regions, and in Iraq is known only in the
steppes. Recent work has shown that the fusion of these two floral
regions takes place approximately along the strip of steppe-desert
transition. There are, however, areas of desert country within the
Irano-Turanian domain, and expanses of steppe in Saharo-Sindian
territory.
Biological Types
Apart from the plants of irrigated soil, the vegetation of Iraq may
be divided into two main categories: (a) a scattered perennial com
munity of low-growing shrubby plants, which persist in a more or
less active state throughout the dry season; and (b) a community of
herbaceous or shrubby plants observable only in the spring or in the
first few months of summer.
(a) An eight months’ drought coupled with blistering heat demands
a high degree of specialization in plants which survive above ground-
level throughout the summer. Such drought-resisting species are
known as xerophytes. By certain modifications of structure, effective
control is exercised over water economy, so that a favourable balance
is maintained between absorption and conduction on the one hand
and loss by evaporation on the other. In Iraq these plants are mostly
low shrubby or sub-shrubby perennials, grey and often seemingly
lifeless at the height of the hot summer, but growing actively and
flowering after the winter rains have moistened the dry dusty soil.
{b) In startling contrast to the dreary vegetation of summer is the
bright herbage of the spring. At this season, when the parched soil
has been moistened by winter rains, and the sun is not too hot, a
varied and colourful society of annual and perennial plants appears.
Annuals may be separated into at least two types. First, there are
the true mesophytes, incapable of resisting drought, which are green
and lush. The short rainy season accelerates their life-cycle, so that
only a few months or even weeks elapse between initial germination
and the setting of seed. These short-lived annuals are known as
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