xlvi INTRODUCTION. 



are capable of enduring great extremes of heat and cold, 

 but will not bear often-repeated alternations of either for 

 long during their rest period. Rockwork formed on the 

 face of a slope or bank may be raised as high as correct 

 taste and convenience v/ill allow, because its position will 

 protect it more or less from the evils hinted at above, and 

 has the effect of disguising the disproportion that exists 

 between the base and elevation. But if it rises from level 

 ground, the elevation of the mass or solid portion will be 

 more beautiful as well as more useful if it is humble. 



The arrangement of the plants will be determined to 

 some extent by the requirements of the different sub- 

 jects as regards sunshine, shade, and moisture ; but in 

 any case it ought to be natural, and as far as possible 

 without design, other than that of producing a beauti- 

 fully-varied and pleasing whole, in which grace of form 

 and colour should freely mingle, the one helping out 

 the effect of the other. As a rule, the larger and more 

 robust subjects should occupy the more elevated, ex- 

 posed, and distant positions ; and the smaller and more 

 delicate ones, those that are nearer the eye, where their 

 less ostentatious attractions may be fully enjoyed. 



The after-management of the plants is simple enough, 

 but entails constant attention. Their peculiar habits 

 must be studied and fostered by every means in the 

 case of the weakly and diminutive, and restrained within 

 due bounds in the case of the strong and encroaching. 

 The enemies of small and delicate species, in the shape 

 of slugs, wire-worms, and earth-w^orms, are numerous 

 and active during spring and early summer, and have to 

 be constantly watched and destroyed. Nothing is better 

 than hand-picking in the case of the slug ; and the even- 



