248 PARKS AND PLEASURE-GROUNDS. 



pose. It is hardly needful to point out the immense dis- 

 ruption of affinities these chasms must cause^ both in 

 the alliances and in the internal structure of the orders. 

 Hence the arrangements of an arboretum can be at best 

 only fragmentary ; but that is no reason for neglecting 

 or disregarding the materials for combination which are 

 within our reach. The fragments that remain to us are 

 capable of assuming a highly scientific form, and so may 

 be invested with attractive interest. 



Now, in planting the trees and shrubs of an arbore- 

 tum we might begin at one end of the classification, it 

 matters not at which, and taking the first genus that came 

 to hand, we might put down its species in a straight or 

 curved line, or double line, and we might proceed to the 

 other genera successively, till we had gone through the 

 whole series, as we would wind ofi* a thread from a reel. 

 The lines might be drawn along a border within the 

 four sides of an enclosure, or might occupy narrow 

 parallel borders, separated by walks, or might assume the 

 form of a spiral, running from the exterior of the space 

 to its centre, or reversely. This is what we have already 

 called the linear arrangement ; but though it has been 

 adopted in some nurseries for the sake of mercantile 

 convenience, it is highly objectionable in various points 

 of view. Not to speak at present of the sacrifice of 

 beauty thus made, it is evident that this collocation pre- 

 serves only the affinities which a genus or order bears 

 to that immediately preceding, and to the other imme- 

 diately succeeding ; and these undoubtedly do not include 

 the whole of its relations. As already noticed. Dr. 

 Lindley, in his ^ Vegetable Kingdom,^ appends to each 

 of his orders an instructive exhibition of its position ; 

 that is, he puts the order in question in the centre, and 



