294 DISEASES OF CULTIVATED PLANTS 



the leaves. Teleutospores are produced from midsummer 

 onwards, as roundish or elongated dark-coloured spots on 

 stem and leaves. The disease is often present in such 

 quantity as to greatly interfere with the yield. 



Uredospores subglobose, ochraceous, aculeate, 17-35X 

 17-25 jx. Teleutospores ovate or subclavate, smooth, brown, 

 apiculus darker and thickened, 24-47x17-30 p, pedicel 

 hyaline. 



A difficult disease to check, as spraying is mostly imprac- 

 ticable. If it is grasped that the disease can only commence 

 in the spring from germinating teleutospores or winter-spores 

 that have passed the winter on old stems and leaves, perhaps 

 all such that are diseased will be collected and burned, 

 instead of being kept, when they are certain to find their way 

 eventually to the manure heap, and thence back to the land, 

 where the spores infect a new crop. Wild vetches should not 

 be allowed to grow in hedgerows, etc. 



Carnation rust ( Uromyces caryophyllinus t Schrdter) often 

 injures or even kills cultivated carnations, and usually spreads 

 with great rapidity unless promptly checked. It forms small 

 brown spots on both surfaces of the leaves, which soon curl 

 and die. It is not a native species, having probably been intro- 

 duced along with plants, and is spread from place to place 

 by the same means. 



Uredospores and teleutospores are often mixed in the same 

 pustule or spore-bed. Uredospores aculeate, 40X17-28/*. 

 Teleutospores subglobose, apex thickened, 23-35 x 15-22 /<. 



Spraying with dilute Bordeaux mixture, if the plants are 

 resting, proves effective. Otherwise sponging with perman- 

 ganate of potassium must be resorted to. 



Beetroot rust ( Uromyces betae, Kuhn) occurs on the 

 leaves of beetroot, sugar beet, and mangold, and when 

 present in abundance, as is usually the case when it once 

 appears, does much injury, checking or completely arresting 

 the work normally accomplished by the leaves, and thus 

 preventing the swelling of the root. The cluster-cup con- 

 dition appears first in the spring under the form of minute 

 whitish clusters grouped on yellow spots. This is followed 

 by the uredo condition, which usually forms small pustules 

 thickly scattered over the entire surface of the leaf. At a 

 later stage the final teleutospore condition follows, the spores 



