May, 1942 
The Queensland Naturalist 
25 
water is unavailable to the plant. 
The desert is a region of extremes. High day-tem- 
peratures may alternate with low night-temperatures, long 
practically rainless periods may be succeeded by short 
periods of heavy rain, while strong winds may be of 
common occurrence. A feature of some deserts and 
nearby regions is the periodic occurrence of dust-storms 
and sand-storms. These should be carefully distinguished. 
In dust-storms only the finest particles of earth are car- 
ried by the wind, often to considerable heights, and to 
great distances. Sand-grains are very much heavier and 
cannot be lifted to any great height and are carried for- 
ward in a peculiar bouncing motion. The entire mass of 
the moving sand, which may be quite dense, is said to 
exceed but rarely 6 or 8 feet in height, and may be con- 
siderably lower. 
As might be expected, plants and animals living in 
deserts have many peculiarities, which enable them to 
exist under such difficult conditions. Plants are usually 
widely scattered since there is not sufficient moisture to 
support numerous plants for very long. In most perennial 
plants of the desert the roots are very long in proportion 
to the size of the plant. Some penetrate the soil to great 
depths where moisture may remain for a long time or 
where it may have seeped a long way from higher 
and perhaps better- watered land. Other roots may 
extend for enormous distances away from the plant so 
that they are enabled to absorb moisture from over a large 
area. The roots, particularly tap-roots, are often thick- 
ened and fleshy, and help to store up water. 
Many desert plants lie flat on the ground, while many 
others form hemispherical or semi-ellipsoid masses, the 
so-called “mat” and “cushion” plants. Annual plants 
may assume these shapes, but the most striking are 
special kinds of shrubs. The main stems of these plants 
are short, but they produce a very large number of 
branches and branchlets all pressed very closely 
together, and bearing tiny leaves (often covered with 
woolly hairs) only at the ends. Cushion plants often 
consist almost entirely of a great mass of wood with a 
thin covering of leaves on the outside. In New Zealand, 
on some of the high mountains, some of these cushion 
plants grow to a large size and are known as “vegetable 
