PLANT DISEASES DUE TO FUNGI. 43 



with the dew on the plant or rain, they germinate, producing germ- 

 tubes which make their way into the epidermal cells, or the sporangia 

 give rise to numerous minute gonidia capable of freely moving about. 

 These settle on the epidermis of the seedling and develop germ-tubes, 

 which make their way into the epidermal cells. 



The sporangia may be carried by the wind, mice, game, and on 

 the clothing of man. 



Later, as the result of sexual process, the oospores are formed in 

 the tissues of the seedling, and by decomposition of the host plant 

 ultimately fall to the ground. 



PREVENTIVE AND REMEDIAL MEASURES. 



All infected plants should be removed and burned as soon as ever 

 the disease is noticed. Seed beds should be carefully examined for 

 any signs of the disease in May and June. 



All contrivances for artificial shading should be removed, in order 

 to permit of the rapid evaporation of moisture. 



When seedlings have been removed in any numbers, the space left 

 should be covered with ground unslaked lime, this being again covered 

 with uninfected soil. This will guard against the spread of the 

 sporangia. 



Seed beds known to be infected should not be used again for 

 several years. 



Spraying with Bordeaux mixture has been recommended, but 

 unless used at the very outset of an attack, is seldom of much use. 



BEET AND MANGEL ROT. 



Sphaerella tabifica, Prill, and Del. 



A case of " Heart Rot ' in mangels \vas reported to me 

 in September last. Fortunately but very few plants were attacked ; 

 these were lifted and burned, and the ground liberally dressed with 

 ground unslaked lime. 



The first signs of the disease is indicated by the wilting of the 

 leaves, which gradually turn yellow and rot away. The fungus present 

 in the leaf stalks appears at this stage as whitish patches bounded 

 by an orange-red border, the whole of the whitish portion containing 



