24 WALL AND WATER GARDENS 



the courses, some of the hardy Opuntias would be par- 

 ticularly suitable ; they are mentioned more at length 

 in the chapters on rock-gardens. Here would also be 

 the most suitable place for the Euphorbias. 



Several of the Edraianthus (now better known as 

 Wahlenbergta), pretty plants of the Campanula family, 

 that are often lost in gardens from winter damp, will 

 be safe in the sunny wall. The best will be W. dal- 

 matica and W. Pumilio. Another branch of the Cam- 

 panulacece, the Phyteumas, are of special value in the 

 wall, and will do nowhere so well. The most usually 

 cultivated are P. comosum, P. hejuisphcericum, and P. 

 orbiculare. Other pretty plants, also often lost in the 

 usual forms of rock-garden, are Acantholhnon venustum 

 and A. glumaceum ; allied to Thrift. 



Many of these plants are best propagated by fresh 

 seed, which can be sown as soon as it ripens in adjoin- 

 ing joints and crevices. It should also be remem- 

 bered that there are several annuals that can with 

 advantage be sown in the wall ; some of the most 

 suitable would be Iberis odorata, Saponaria calabrica^ 

 and Silene pendula, also the little blue Stonecrop 

 {Sedum caeruleum). 



The lovely little Petrocallis pyrenaica is a true plant 

 for the sunny wall in its upper joints. The larger 

 growth of StobcBa purpurea will also suit the top joints 

 of the upper courses, or the warm place at the wall- 

 foot. It is a thing that will not only do well in such 

 places, but that so used will look quite at its best. To 

 those who are unacquainted with it it may be described 

 as a thistle-like plant with silvery-green spiny foliage 



