260 PLANT DISEASES 



seven to ten cells, dark brown, and minutely warted : stalk 

 long, colourless, swollen near the free end. 



PREVENTIVE MEANS. Spraying with potassium sulphide 

 solution checks the extension of the rust. If Bordeaux 

 mixture is used it should be very much diluted, otherwise 

 the foliage will be injured. If the disease has run its 

 course, the fallen leaves should be gathered and burned to 

 prevent a recurrence of the disease. 



Prillieux, Malad. des Plantes Agric., vol. i. p. 251. 



ROSE RUST 



(Phragmidium subcorticatum, Winter.) 



A troublesome pest to cultivators of roses, attacking 

 more especially hardy hybrid varieties. All three forms of 

 the fungus are produced on the same host. The aecidia 

 appear in late spring on the leaves and young shoots, form- 

 ing powdery, orange patches, and often cause distortion of 

 the shoots. About midsummer the patches become deeper 

 in colour, owing to the formation of uredospores. Finally 

 the teleutospores or resting-spores are produced as minute 

 black dots on the under surface of the leaves. 



PREVENTIVE MEANS. The appearance of the disease in 

 spring depends entirely on the presence of teleutospores in 

 the neighbourhood ; it is therefore necessary to collect and 

 burn all fallen leaves in the autumn. Plants that have been 

 attacked the previous season should be thoroughly drenched 

 with a solution of sulphate of copper in water 2 ounces 

 in 3 gallons in early spring before the buds expand. The 

 soil round the plants may also be sprayed with the same 

 solution. Dilute Bordeaux mixture, or ammoniated car- 



