72 THE CULTURE OF POT-PLANTS 



are rather numerous, and include aphides, thrips, red spider, 

 earwigs, the grubs of the carnation fly, eelworms, and, 

 among fungoid diseases, mildew, rust, and spot. For aphides, 

 thrips, and red spider (a sure sign of excessive dryness) the 

 plants should be syringed with an insecticide. Earwigs should 

 be trapped in short lengths of hollow bamboo. Eelworms, 

 too small to be seen with the naked eye, cause swellings on 

 the stems, and eventually kill the plants, which, in the case 

 of a bad attack, should therefore be burned. The soil also 

 should not be used again or thrown away to infect the land, 

 but should be sterilised by baking or by pouring formaldehyde 

 over it. If sterilisation is performed before the soil is used 

 for carnations (see p. 30), the trouble can be prevented. The 

 grubs of the carnation fly cause white streaks in the leaves. 

 The insect can be extracted with a pin, and if the plants are 

 syringed with water containing a dash of paraffin, the flies 

 will be kept away. For the fungoid diseases a weak solution 

 of permanganate of potash may be used ; but spot, character- 

 ised by pale rings on the leaves and stems, if allowed to 

 develop as the result of unsuitable conditions, resists every 

 known treatment and is almost sure to destroy the plants. In 

 the case of an outbreak, therefore, it is better to sacrifice any 

 that have been severely attacked. When the disease is only 

 slight, a cure can sometimes be effected by removing the 

 damaged leaves. 



Chimonanthus fragrans. — A slender shrub which 

 usually needs support, the flowers very fragrant. It is hardy 

 enough to be growm in the open air, but the flow^ers last 

 much longer when they are protected from the weather. As 

 it flowers on the wood of the previous year, it should be cut 

 back rather hard immediately after flow^ering in order to 

 induce as many shoots to start as possible. 



Chionodoxa.— See Bulbs, p. 136. 



Chrysanthemum (Japanese). — See p. 51. 



Coleus thyrsoideus. — A handsome species with blue 

 flowers borne in winter in a warm greenhouse. When they 

 are open the plants can be brought into a room. Propagation 

 by seed and cuttings. See Coleus, p. 120. 



