226 SCIENCE OF THE STUDY OF TREES. PART II. 



plants, are not many ; but, still, some, such as the canker, &c., require to 

 be noticed, when the species subject to them come under review. 

 D. Accidents. Some trees and shrubs are more liable than others to be 

 blown down, or have some of their branches broken off by high winds, or 

 by the weight of snow ; and these species should be pointed out to the 

 inexperienced planter. Some, also, are said to be less liable to be struck 

 by lightning than others ; for example, the beech. 



7. Geographical Distribution. The different countries will be mentioned where 

 each species is found naturally ; and, where practicable, the different lo- 

 calities, soil, elevation, and other particulars will be given. It will also be 

 stated, as far as is known, in what countries each species is cultivated, and 

 to what purposes it is applied. 



8. History. This subject may be included under two heads ; viz. retrospective 

 and prospective. 



A. The Retrospective History of every species or variety will commence 

 with its first discovery, or record by botanists ; and its progress will be 

 traced in every country, but more especially in Britain, from that period 

 to the present time. Though the history of some trees and shrubs com- 

 mences with the time of the Romans, yet that of others is comparatively 

 obscure ; and, of some of the finest ornaments of our gardens, little more 

 can be stated than that they are races or varieties, perhaps hybrids, raised 

 by cultivators whose names are unknown. 



B. The Prospective History, or probable progress, of our knowledge of 

 species may be included under the heads of doubtful species, unnamed 

 species, and expected additions. 



a. Doubtful Species. In almost every genus, containing several species, 

 there are some of the names which are of doubtful application, which 

 under this head we shall bring together, with their authorities, in order 

 to direct the attention of botanists and cultivators to the subject. 



b. Unnamed Species. The introduction of new species of trees and 

 shrubs into British gardens is constantly going on, and numbers are also 

 as constantly being raised from seed in the country. In general, neither 

 of these kinds of additions to our ligneous flora can be received into 

 books till they have flowered ; when they are named, figured, and re- 

 corded in some botanical work. It often happens, however, that the 

 genus to which a new plant belongs is discovered, from the general 

 habit of the plant, long before it has flowered ; and in such a case, 

 though the species may not be introduced into botanical catalogues, 

 plants of it may be distributed among cultivators by those who have 

 introduced it, and it may be propagated for sale in the nurseries, under 

 some provisional name. Such species, and also varieties raised in the 

 country from seed, or otherwise procured, deserve notice in a work 

 like the present, and we shall devote this head to the subject. 



c. Ejected Additions. The species of some genera are so numerous, 

 and their geographical distribution is so extensive, that from these cir- 

 cumstances alone we may reasonably anticipate the discovery and 

 the introduction of additional species. Of other genera, many species 

 suitable for our climate, though not yet introduced, have been described 

 by botanists as indigenous in different parts of the temperate hemi- 

 spheres. It will be useful to direct attention to both these points, with 

 a view of stimulating travellers and others to procure the additional 

 species that are known ; and wealthy individuals, or societies or asso- 

 ciations, to send out collectors to discover those species which may be 

 yet unknown. 



9. Use. Trees and shrubs are used in the arts of construction, of machinery, 

 and of fabrication ; in the chemical arts of dyeing and colouring ; in domestic 

 and rural economy ; and in medicine. 



A. The Arts of Construction are, civil, military, and marine architecture ; 

 engineering, carpentry, joinery, cabinet-making, carving, and modelling ; 



