THE TYPES OF ROCK GARDEN 15 



want of air which causes plants to damp off, 

 especially during the winter. The only occasion 

 on which this form of quarry is admissible is 

 when it is on a very large scale, at least 25 

 yards across, and even then it will generally 

 prove but a doubtful success. 



The next and perhaps the commonest form 

 is the semicircle or horseshoe^ usually an excava- 

 tion into the side of a hill, giving bold rocky 

 places for planting. This is an excellent form 

 to choose, provided it fulfils certain conditions. 

 It should not open towards the north, for then 

 it would be exposed to the cold winds and 

 the greater part of the rocks would constantly 

 be in shade, and although some shady corners 

 will be found useful, the majority of plants 

 like the sun. In fact, any point but this will 

 do, for so long as the entrance is sheltered 

 from the north it is a matter of no great 

 importance where it may be ; but the south- 

 east is preferable, for it gives greater variety 

 of position, both for sun- and shade-loving 

 plants. 



The valley or defile form can be made very 

 effective. The best way for it to lie is east 



