54 DISEASES OF TROPICAL PLANTS 



CH. 



The various species of the genus Alternaria are also 

 the cause of many diseases. The conidia are muriform, 

 many-celled, and borne in chains on the tips of simple 

 or branched conidiophores. Among the most important 

 are A. citri of the orange, and A. castilloae of the 

 rubber. 



The genus Macrosporium bears a close resemblance 

 to the genus Altenaria, but the conidia are solitary 

 instead of in chains. Among the most important are 

 the M. Solani, E. & M., which causes the early blight 

 of the potato and tomato (pp. 209, 217); M. nigri- 

 caulitum, Atk., of the cotton ; M. commune, Eafeul, 

 of the tea; M. longipes, E. & E., and M. tabacinum, 

 E. & E., of the tobacco. 



The species of Cercospora are the cause of a very 

 large number of leaf-spot diseases, and are very common 

 and abundant in both tropical and temperate countries. 

 The conidia are very much elongated, slender and many- 

 celled, and are readily recognised. Among the most 

 important are C. beticola, Sacc. , of the beet ; C. apii, 

 Fr., of the celery ; C. gossypina, Cke., of the cotton ; 

 C. longipes, Butler, C. sacchari, (Br.) D. & H., C. 

 vagina, Kr., C. acerosa^ D. & H., and C. Jcopkei, 

 Kr., of the cane; C. sorghi, E. & E., of the corn; C. 

 nicotianae, E. & E., and C. raciborskii, of the tobacco ; 

 C. coffeicola, B. & C. (Fig. 33), of the coffee; C. 

 personata, Ellis, of the peanut ; C. viticola, Sacc., of 

 the grape ; C. hibisci, Tracy and Earle, of the Okra ; 

 C. theae, van Breda, of the tea ; C. bolleana (Thum) 

 Speg. , of the fig ; and many others. 



The genus Helminthosporium also contains many 

 parasitic species. The conidia are cylindrical or spindle- 

 shaped, and many-celled. Among the most important 

 are H. heveae of the Para rubber, H. theae of the tea, 

 and a number of species on corn and other grains. 



Family Stilbaceae, which are mainly saprophytic. 



Family Tuberculariaceae, which contains the genus 

 Fusarium, which is the cause of many severe diseases. 



In the genus Fusarium (Fig. 34) the conidia 



