42 



THE CULTURE 0¥ POT-PLANTS 



the plants are kept too wet, they are liable to decay at the 

 collar. If at any time they are allowed to get excessively 

 dry, they are almost sure to be infested with aphides (green- 



FiG. 17. — Primula sinensis, soil heaped round the base to induce 

 the plant to form rooted offsets. 



fly), which are not easy to get rid of because of the difficuhy 

 of spraying underneath the leaves, where the insects con- 

 gregate. It may be necessary to apply an insecticide with 

 a brush. A fungoid disease sometimes causes white, brown- 

 edged spots on the leaves. To prevent its spreading a very 

 weak solution of permanganate of potash should be used. 

 Primulas are best grown in partial shade. Their flowers will 



