90 THE VEGETABLE WORLD. 
present a still more considerable number of trees always green. 
It must not be supposed, however, that in the tropics all the trees 
are evergreens. Even in the vast forests which occupy the 
Brazilian coast, and where vegetation is maintained in continual 
activity by its two principal agents, heat and moisture, there exist 
trees, such as some of the Begnoniacex, which lose every year, like 
- our trees, all their leaves at once, but immediately after they are 
covered with flowers, and in a very short time these are succeeded 
by new foliage. I speak here of woods growing in equinoxial 
regions, where, as with us, rain and drought have no determinate 
period. In countries, on the other hand, where six months’ 
continual rain is succeeded by uninterrupted dry weather, there 
are woods which every year remain for a considerable time 
destitute of verdure, and the traveller who traverses them 18 
scorched by the ardent blaze of the equinoxial zone, while he has 
before his eyes the leafless image of European forests during 
winter. We have even seen this excessive drought continue during 
two years, and the trees remain for two years without their foliage.” 
But evergreen trees are only exceptional in the vegetable world. 
Most trees, shrubs, and herbaceous plants are without their leaves 
during one half the year. When the leaves have performed their 
functions, when the fruits have appeared, matured, and ripened, 
vegetation has entered into a new phase; the leaves lose their 
brilliant green and assume their autumnal tint, sometimes clothed, 
however, in colours of accidental, though transitory, brightness. 
e green, when it is persistent, is more grave and sober in its 
hue ; it becomes brown in the Walnut, it takes a whitish tone ™ 
the Honeysuckle. The leaves of other plants, as the Ivy, the 
Sumach (Rhus Cotinus), the Dog-wood tree (Cornus), become 
clothed in a reddish tint; they become yellow in the Maple (Acer 
campestre), and many others of our forest trees. But whatever 
may be the variety of shades which leaves take in their decay, a 
certain air of sadness pervades these ornaments of our fields, which 
proclaims their approaching dissolution, and betrays the imminence 
of the cold season. Oold and humidity will soon arrest the SP 
and disorganise the petiole ;,the leaves, withered and deformed, 
will soon cumber the ground, to be blown hither and thither by : 
the wind. It is the season of the fall of the leaf with all 1° — 
