56 DISEASES OF TROPICAL PLANTS CH . 



In the genus Oospora the mycelium penetrates the 

 host, but eventually emerges to produce the chains of 

 transparent or slightly coloured, globose, one-celled 

 conidia. The most important disease caused by Oospora 

 is the potato scab, caused by 0. scabies, Thaxter (page 

 280). 



The species of the genus Ramularia attack many 

 plants. The conidiophores emerge from the stomata, 

 forming tufts, and bear numerous terminal conidia. 

 The most important diseases are the " areolate mildew " 



FIG. 34. Conidiophores and spores of Fusarium species. 

 (After Cook and Home, Bui. 7, Estacitn Central Agronomica de Cuba.) 



of the cotton, which is due to R. areola, Atk. (see page 

 112), and R. necator, Massee, of the cacao. 



In Piricularia the conidia are many-celled and 

 borne on unbranched conidiophores. The most im- 

 portant disease due to this genus is P. grisea, (Cke.) 

 Sacc., of the rice (see page 99). 



Pellicularia kaleroga, Cooke, of this order is one of 

 the well-known fungi of the coffee ; Necator decretus, 

 Massee, is the cause of an important disease in the tea ; 

 Coniothecium scabrum is the cause of a disease on citrus 

 fruits ; C. cqffeae, of the coffee ; Pucciniopsis caricae, 



