38 PLANT ASSOCIATIONS 
(a dry area) with that of Middle Europe or of England, 
we shall be struck with the prevalence in the former 
of small-leaved twiggy plants—Lavender (Lavanduia) 
and Rosemary (Rosmarinus officinalis) will serve as 
examples. Often leaf-reduction is carried much 
farther, and we need not go beyond our own commons 
to find a good example, for in the Gorse (Ulex) 
flat leaves are entirely absent and the branches are 
shortened and converted into prickles, thus largely 
reducing the surface exposed to the sun and wind. 
The seedling Gorse has little trifoliate leaves, which 
remind us of its affinity to the Trefoils and Brooms, 
but they are discarded almost at once, to fit the plant 
better for life in the dry, breezy localities which it 
favours. Reverting to the Mediterranean flora, a 
characteristic of its plants is the prevalence of a grey 
hue in their stems and leaves, such as we see in the — 
Pinks and Achilleas of our rock gardens. This is due 
to a coat of wax, as in the Pinks (Dianthus), or a felt 
of hairs, as in the Achilleas, designed to check exces- 
sive transpiration. The coatings of hairs are often 
of great beauty and complexity, and form an almost 
impenetrable covering to the leaf surface, protecting 
the upper side from the fierce rays of the sun, and on 
the underside sheltering the stomata, or minute open- 
ings through which the plant exhales the surplus 
water drawn up from the roots and inhales carbon 
dioxide. Another very beautiful device for protecting 
the underside of the leaf, and one which may be 
studied in many of our commonest plants, consists of 
the inrolling of the edges, often combined with a 
wrinkling or ridging of the underside, so that the 
stomata are set in deep hollows, communicating with 
