NEW AND BEAUTIFUL ROCK PLANTS 91 



on top of which they go out of flower, leaving them some- 

 what of a burden. It is wise to substitute the double 

 for the single, as it is less rank and flowers longer ; this 

 useful plant may be propagated by cuttings in boxes 

 of sandy soil in early summer and planted out in autumn ; 

 there is now a variegated leafed form of it. Albida 

 variegata is a variety of the common with a white- 

 edged leaf, and as it is a more compact grower it is better 

 for the rockery ; it is a pretty and desirable plant. Sturii 

 is a small, white-flowered species. One of the most 

 interesting and beautiful of the Rock Cresses is aubrie- 

 tioides, which is of dwarf compact habit, and bears a 

 profusion of beautiful pink flowers ; this is good enough 

 for the choicest collection of Alpines. Billardieri re- 

 sembles it closely. The Rock Cresses thrive in ordinary 

 soil, and are easily propagated by seeds, cuttings and 

 division. See also the remarks in another chapter on 

 the use of Arabises and Aubrietias with bulbs in borders. 



ARENARIA (SAND WORT) .The best-known species 

 is Balearica, a creeper with small white flowers. It is 

 a pretty plant, but montana, while it is also a good 

 carpeter, has larger flowers ; it likes a sunny, rather dry 

 soil. Propagation is by division. 



ARMERIA (THRIFT). The well-known edging plant 

 is maritima. Csespitosa is a pretty miniature species 

 with pink flowers, suitable for the rockery. 



ARNEBIA (MACROTOMIA) ECHIOIDES. The pretty 

 " Prophet Flower," with its spotted yellow flowers, 

 should be planted ; it is one of the best of the summer 

 bloomers. 



AUBRIETIAS. In its mountain home the Grecian 

 Rock Cress is secure from comparison with the new 



