ROCK AND ALPINE PLANTS 137 



washing is imperative. The following ob- 

 servations on such rock and Alpine plants 

 as have been found most suitable for planting 

 in a town garden are the result of many years 

 of study and experiment, and have, in the 

 main, been collected from several of the most 

 smoke-infested parts of London and other 

 large cities. Probably the best all-round 

 plants for the rock garden are the various 

 species of dwarf Iris, many of which will not 

 only succeed but absolutely flourish, where soot 

 and smoke are the order of the day. In cor- 

 roboration of this we have only to visit some 

 of the gardens in the East End of London, 

 or at Lambeth and Bermondsey, and see how 

 well these plants are suited for doing battle 

 with the impurities of a town atmosphere. 

 In the grounds of the Royal Mint or in the 

 gardens attached to the Tower of London, 

 where the atmospheric conditions are too well 

 known to require comment, the various kinds of 

 Iris flourish amazingly. Even in *dry, poor soil, 

 the appearance of which strikes one as sooty in 

 the extreme, the commonly cultivated species 



