116 WOOD AND GARDEN 



much else, one must watch what happens in one's 

 own garden. We practical gardeners have no absolute 

 knowledge of the constitution of the plant, still less 

 of the chemistry of the soil, but by the constant 

 exercise of watchful care and helpful sympathy we 

 acquire a certain degree of instinctive knowledge, which 

 is as valuable in its way, and probably more appli- 

 cable to individual local conditions, than the tabulated 

 formulas of more orthodox science. 



One of the best and simplest ways of growing rock- 

 plants is in a loose wall. In many gardens an abrupt 

 change of level makes a retaining wall necessary, and 

 when I see this built in the usual way as a solid 

 structure of brick and mortar — unless there be any 

 special need of the solid wall — I always regret that it 

 is not built as a home for rock-plants. An exposure 

 to north or east and the cool backing of a mass of 

 earth is just what most Alpines delight in. A dry 

 wall, which means a wall without mortar, may be any- 

 thing between a wall and a very steep rock-work, and 

 may be built of brick or of any kind of local stone. I 

 have built and planted a good many hundred yards of 

 dry walling with my own hands, both at home and in 

 other gardens, and can speak with some confidence both 

 of the pleasure and interest of the actual making and 

 planting, and of the satisfactory results that follow. 



The best example I have to show in my own 

 garden is the so-called " Old Wall," before mentioned. 

 It is the bounding and protecting fence of the Pseony 



