THE FUNGI WHICH CAUSE PLANT DISEASE 495 



hyphffi, rostrum, 20-30 fi long, apically fimbriate; conidia globose- 

 elliptic, 5-9 II. 



The fungus grows in the sweet potato producing dark, almost 

 black spots in the skin. The tissue below becomes olive-green. 

 The dark mycelium is found penetrating 

 through and between cells of the dis- 

 eased area where numerous olivaceous 

 conidia are also present. The elon- 

 gated beaks of the pycnidia rise like a 

 small forest from the surface of the 

 potato. 



In artificial culture the mycelium is 

 dark, abundantly septate and with nu- 

 merous oil globules. Long multiseptate 

 eonidiophores with light colored tips Fia. 340.— S. fimbriatum; i, 

 arise from the medium. From these pycnidium sending forth 



. . spores; 2, hyaline comdia; 6, 



hyalme conidia are produced, appar- olive conidia. After Halsted 

 ently endogenously. Fig. 340, Oliva- 



ceus, globose to elliptical. Fig. 340, conidia are formed within the 

 medium on branches of the mycelium in much the same manner. 

 The pycnidia develop in about nine days after inoculation and the 

 conidia are extruded from the fimbriate mouth of the long ros- 

 trum. 



Inoculations proved the pathogenicity of the organism, 

 typical black rot appearing in about three weeks after infec- 

 tion. 



S. adiposum Butler causes a black rot of sugar cane. 



S. pomarum Sh. is on cranberry. 



S. spurium (Fr.) Sacc. on Prunus is often reported as Dematium 

 prunastri. 



S. oryzae Miy. is on rice." 



Chsetophoma Cooke (p. 482) 



Pycnidia superficial, very small, on a subicxilum of interwoven 

 hyphse; conidia ovate or elliptic, very small. 

 Some forty species, chiefly American. 

 C. glumanim Miy. parasitizes rice in Japan. '^ 



