FUxNGOID DISEASES OF POTATOES 8i 



any visible appearance of the fungus (Fig. 23, A) ; 

 later, dark patches consisting of masses of conidia 

 are seen. These conidia are dark coloured, irreuu- 

 lar in form, and multicellular. 



B 



Fig. 23. — (A) Potato leaflet sufteringfrom Leaf Curl ; notice the irregular 

 spots with concentric rings ; (B) club-shaped septate spore of Macro- 

 sporhim solani with germ tubes from some of the cells; (C) peculiar 

 forms of spores ; (A) slightly reduced ; (B and C) magnified ; (B and C) 

 after Jones, 



Cause. — The cause of the disease is the presence 

 of the fungus J/, solani. Its mycelium, which is 

 dark in colour, destroys the leaf tissue, sometimes 

 resulting in curling, and forms later, large conidia 

 on simple, or branched, conidiophores. (Fig- 23, 

 B and C.) 



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