64 
EVERGREEN AND DECIDUOUS TREES, ETC. 
(1.)—Evergreen trees and shrubs are most abundant 
within the zone extending about 45° on either side of the 
equator, and having in no part of it, except on the mountains, 
a mean annual temperature of less than 50°. Within this 
zone, the evergreens form probably 80 per cent, of the total 
number of species, and in some parts of it a deciduous tree 
or shrub is scarcely to be found. 
Deciduous trees and shrubs predominate in the zone, 
extending from about 45° to 60° of latitude, having a mean 
annual temperature of not less than 40°. Within this zone, 
they would constitute probably 80 per cent, of the total 
species if it were not for the Coniferse, whose 200 evergreen 
species occur chiefly in this region. 
(2.)—The whole of the Conif'erae are evergreen w r ith the 
exception of the Larch, the Salisburia, and one or two others. 
(8.)—A few species of trees and shrubs are evergreen in 
their native homes, but deciduous in more severe climates, 
as Ligustrum Japonicum, Cotoneaster Simmonsii, and some of 
the Cistuses. 
(4.)—Certain orders, as Cornaceae, contain some genera 
which are evergreen (Aucuba, Garry a, &c.), and others which 
are deciduous (Cornus). Many genera, as Berberis, Viburnum , 
&c., contain some species which are evergreen, and others 
which are deciduous ; and some deciduous species produce 
evergreen varieties, as Ligustrum vulgare , var. sempervirens. 
(5.)—There are about 8,600 known species of evergreen 
trees and shrubs, and about 1,200 deciduous species. About 
75 per cent, of each bear showy flowers. Taking the whole 
4,800 together, about 3,600 are shrubs and 1,200 trees. 
(6.)—The hard cuticle of many evergreen leaves minimises 
evaporation, and their upper surfaces are often quite destitute 
of stomata. 
(7.)—The young shoots of hardy evergreens in this 
country commonly remain green on one side, if not all round, 
throughout the winter, while those of deciduous species are 
mostly brown, plum-colour, or black. 
(8.)—Professor Hillhouse, in a paper read before the 
British Association at Birmingham, has incidentally shown 
that deciduous leaves when they fall in autumn leave an 
accumulation of starch or other reserve food round the base 
of the dormant bud. This is not the case with evergreens. 
The chlorophyll-grains in evergreens leave the cell walls in 
winter and unite in central masses, but do not become de¬ 
composed as in deciduous leaves. 
(9.) — Starch is only developed from chlorophyll under the 
influence of light. If it remains in contact with chlorophyll 
