60 DISEASES OF TROPICAL PLANTS CH . 



In the genus Hendersonia the pycnidia are sub- 

 cutaneous. Among the most important of the tropical 

 species of this genus is H. tlieicola, Cooke, which 

 attacks the tea, and H. coffeae, Del., which attacks the 

 coffee. 



In the genus Actinonema the pycnidia are very 

 small, and the conidia are clear and two- or three-celled. 

 In this genus we find A. rosae, (Lib.) Fr., on the rose, 

 and many other diseases. 



In the genus Septoria the pycnidia are very much 

 like those of Phyllosticta and Sphaeropsis. The spores 

 are clear, long, usually multicellular, and frequently 

 slightly curved, and bear some resemblance to those of 

 Cylindrosporium. The species of this genus are the 

 cause of a very large number of diseases. Among the 

 most important are S. petroselini, Desm., var. apii, 

 Br. and Cav., of the celery ; Septoria lycopersicae, 

 Speg. , of the tomato ; S. theae, Cav. , of the tea ; S. 

 nicotianae, Pat., on the tobacco. 



In the genus Diplodia the pycnidia are small, 

 spherical, and dark-coloured, and the conidia are two- 

 celled when mature. In this genus we find D. cacaoi- 

 cola, P. Henn., which causes the twig disease of the 

 cacao (see page 180), and which also grows on the cane, 

 mango, and other plants ; D. zebrina, of the rubber ; 

 an undetermined species on palms ; D. vasinfecta, 

 Petch, which is the cause of an important disease on 

 the tea ; and D. rapax on the rubber. 



The closely related genera Lasiodiplodia contains 

 L. theobromae, (Pat.) Griff, and MaubL, which is the 

 cause of an important disease of the cacao ; L. 

 tubericola, E. and E. , on mango and cacao ; and 

 Botryodiplodia elastica, Petch, on the rubber. 



In the genus Vermicularia the pycnidia are em- 

 bedded among a mass of brown septate hairs. The 

 conidia are unicellular, occasionally two - celled, and 

 usually spindle-shaped. In this genus are found V. 

 ipomoearum, Schw., of the sweet potato; V. micro- 

 chaeta, Pass., on Camellia japonica in Italy; V. 



