NORTHERN ZONE OF COLD WINTERS 185 
summers are not so dry as to parch the vegetation. The 
plant-associations are very numerous, and may be grouped 
into classes, e.g. forests, heaths, meadows, &c. They are 
largely mesophytic. 
The forests occupy vast areas in this zone, though much 
reduced by man’s operations in modern times. The chief 
elements are the Conifers (Abies, Pinus, Larix, &c.), mostly 
with evergreen xerophytic leaves (Larix, the most northern 
form, is deciduous), the catkinate families (Fagaceae, 
Betulaceae), Acer, Tilia, Fraxinus, &c. Many of these are 
of social habit, and form homogeneous forests, of one species 
only, in certain regions, e.g. pine, birch, beech, &c. All but 
the Conifers are deciduous. The undergrowth of such 
forests consists of young trees of the same species, and of a 
few shrubs and small woody climbers (e.g. Lonicera); on the 
soil grow ferns (never arborescent), grasses, and various 
herbs. The latter are characterised by their early develop- 
ment in spring, before the trees are in full leaf, so that they 
obtain the maximum of available light. Familiar instances 
in Europe are the primrose, violet, hyacinth (Scilla), Adoxa, 
Anemone, &c. Later in the year the saprophytic plants 
(Monotropa, Neottia, &c.) appear. Epiphytic phanerogams 
do not occur, but in very moist places ferns are often 
epiphytic, and the tree-bark is usually covered with algae, 
lichens, liverworts, &c. Other associations are the copses 
of small trees and larger shrubs, such as willow (Salix), hazel 
(Corylus), hawthorn (Crataegus), &c. 
Another class of associations is that of the heaths, 
which cover immense areas in some parts of this zone. 
The chief plants are the Ericaceae, Calluna, Erica, and 
Vaccinium ; others are gorse (Ulex), Ledum, Salix sp., &c. ; 
among these occur grasses and other herbaceous plants. 
Most of these plants are decidedly xerophytic. Hydro- 
phytes, on the other hand (see above), are also common 
in this zone, lakes, rivers, and marshes abounding. 
This zone also contains numerous associations, in which 
the Gramineae (or in wet ground the Cyperaceae) dominate, 
forming a turf ; amongst them grow numerous herbaceous 
plants, e.g. many Compositae, Campanulaceae, Labiatae, 
Scrophulariaceae, Umbelliferae, Onagraceae, Leguminosae, 
Geraniaceae, Cruciferae, Carophyllaceae, Ranunculaceae, 
