DISCRIMINATIVE TREATMENT OF SURFACES. 329 



are usually called American shrubs. On the other 

 hand, it may be ascertained, with some degree of cer- 

 tainty, that the low, damp space referred to would 

 prove injurious to the more tender pines, cistus, mag- 

 nolias, and arbutus. The diversities of climate arising 

 from differences in exposure and .evaporation, even 

 within the limited space of a dozen acres, is often very 

 considerable. We are aware, that to attend properly 

 to these and similar considerations is no easy matter ; 

 but they do not on that account lose their importance, 

 and they should, if possible, receive the attention 

 which is due to them. 



In an arboretum arranged on strictly botanical prin- 

 ciples, there is an invariable deficiency of the effect 

 produced by evergreen trees, as these valuable means 

 of decoration are mostly confined to Orders 3 and 4, 

 viz : Goniferce and Taxacece, and in the method pro- 

 posed they are all placed in one locality. To counter- 

 act or contrast with the bare and impoverished aspect, 

 during winter, of, the deciduous tribes which pervade 

 the arboretum, we would recommend the severance 

 of these evergreen orders into generic, or even sub- 

 generic groups, which, if properly distributed and 

 connected, would tend to relieve the effect adverted 

 to, without their losing, to any considerable extent, 

 their rightful position in their own orders. But even 

 if their ordinary continuity were to suffer interruption, 

 it were better that it should be so, than that they 

 should all be confined to one place. "We also recom- 

 mend the employment of the ordinary evergreen shrubs 

 as promiscuous underwood, in many of the tall decidu- 

 ous groups ; this will not materially affect their scien- 

 tific character, while it imparts to the whole grouping 



