2i2 ROCK GARDENING FOR AMATEURS 



peculiarly liable to damp off. They should have a dry, 

 warm position in sandy soil; they dislike much wet in 

 winter, hence some growers cover them with glass at 

 that season. C. holosericea is the best, hardiest, and 

 most easily grown. Others are C. Mackayi, C. gran- 

 diflora, C. coriacea, C. Lindsayi, C. spectabilis, and 

 C. Munroi. Seed may be sown under glass in spring. 



Cerastium (Snow in Summer). The Cerastiums are 

 native of European mountains, and found also in Britain ; 

 they belong to the Pink family (Caryophyllaceae). They 

 are dwarf plants, soon spreading into large tufts and 

 flowering in May and June. Plants look especially well 

 when inserted in the crevices of an old wall or on some 

 rocky mound, so that their growths may hang down, or 

 they are suitable for planting near the margin of the walk. 

 They should not be placed close to choice alpines. Often 

 they spread so rapidly as to necessitate severe cutting 

 back, which is best done as soon as the flowers are over. 

 The most useful sorts are tomentosum and Biebersteini, 

 with grey leaves and white flowers ; arvense and its 

 varieties compactum and grandiflorum, producing dwarf 

 masses of green foliage, having small white flowers in 

 early summer. Propagation is most readily effected by 

 pulling off rooted portions, which establish themselves 

 quickly. Ordinary well-drained soil, the poorer the better, 

 is suitable, but a sunny spot should be chosen or the 

 plants become weedy and straggling. 



Ceratostigma plumbaginoides. See Plumbago Larpentae. 



Cheiranthus (Wallflower) The Alpine Wallflowers, 



