6 INTRODUCTION. 
The second reason why we have included a number of half- 
hardy, or supposed half-hardy, trees and shrubs in this Work is, 
that we think there are few scenes in an ornamental garden 
or pleasure-ground of greater interest to a person having any 
knowledge of botany, however slight, than a conservative wall ; 
that is, a wall covered with trees and shrubs, natives of foreign 
climates, which, though they may be killed to the ground during 
winter, yet exhibit a degree of luxuriance during the summer 
season, which they never can display in our green-houses or 
conservatories. Even were all such plants to be killed by frost 
every winter, and a reserve obliged to be kept in green-houses 
or pits to supply their place every spring, still, the splendour of 
their appearance during the summer months, and the novelty of 
their forms when compared with those of the spring, usually 
grown in the open air in Britain, would far more than compen- 
sate for the trouble incurred. When we take into consideration 
how easy it is to have such walls flued, and to heat the borders 
in front of them by small pipes of hot water, the capacities of a 
conservative wall and border appear great beyond anything we 
can at present calculate on; and we are persuaded that, were the 
subject of conservative walls warmly taken up by a spirited and 
wealthy individual, something would be produced in this way, 
as superior to our present green-houses and conservatories, as 
these are to the orangeries and green-houses of the time. of 
Evelyn, or even of Miller. Having thus given our reasons for 
the introduction of half-hardy species of trees and shrubs into 
this Work, we shall next submit a few words with respect to our 
arrangement and treatment of the hardy species. 
The general arrangement of the Arboretum et Fruticetum 
Britannicum will be that of the natural system; by which, 
whether in botany, zoology, or mineralogy, those objects are 
brought together which resemble one another in the greatest 
number of particulars. In describing each species, we shall fol- 
low the summary of particulars laid down in the last chapter of 
Part II.; giving in succession the identification of the name by 
botanists; the synonymes, botanical and vernacular; references 
to published engravings; the specific character; the popular 
description; the geography; the history; the poetical and le- 
gendary allusions; the properties and uses; the soil and situ- 
ation; the propagation and cultun@§# the accidents and diseases 
which the plant is liable to; the insects and parasitic plants which 
inhabit it; examples of its growth in the British Islands and ~ 
on the Continent; and, lastly, its price in some of the principal 
British, Continental, and American nurseries. 
In identifying the name of every species, or variety, with that 
given to it by botanical writers, we have been guided principally 
by our own examination of the living plant, and comparing it 
