88 THE BOOK OF THE WILD GARDEN 



amazingly. But one only sees Nature's successes and 

 knows nothing of her failures. Indeed of these latter 

 she is heedless, " so careful of the type she seems, so 

 careless of the single life," and man may well take 

 heart of grace if his expectations be but half fulfilled. 



Old walls in which the mortar has perished may be 

 prepared for the reception of plants by the removal of 

 some of the mortar and replacing it with a gritty com- 

 post in which seedlings may be planted or seed sown. 

 Where walls are being built these should be constructed 

 of large, flat stones, each layer being surfaced with a 

 thin coating of compost which should also be worked 

 well down between the stones and planting should be 

 done as the work proceeds. A retaining wall, that is 

 to say a wall built against a higher level of earth, such 

 as occurs in terraces, offers the best conditions for the 

 satisfactory growth of the plants, as they are able, after 

 penetrating the compost between the stones with their 

 roots, to push these deeply into the soil lying at the 

 back of the wall. Where a wall is to be built on level 

 ground it should be formed of two separate walls with 

 a space of from eighteen inches to two feet between 

 them, which must be filled with soil, tightly rammed 

 down, as the courses are laid. In building a dry wall, 

 the upright surface should slope slightly backward from 

 base to top, and the stones should not be laid quite 

 level but should be a trifle higher in front than at the 

 back. When constructed in this manner rain, instead of 

 running down the face of the wall into the earth at the 

 base, finds its way into the horizontal interstices between 

 the stones, and, 'running backward down the slight 

 slope, moistens the roots of the plants. 



Many subjects suitable for walls have been referred 

 to in dealing with " Dwarf-growing Plants," and these 

 will consequently only be mentioned by name in the 

 following list. 



