344 



FUNGOUS DISEASES OF PLANTS 



organism as the one here described. It was also thought by these 

 French observers that a Sphaerella which was found associated 

 with the Phyllosticta might be a perfect stage of the latter species. 1 



Pycnidia are produced over practically all the deacl portions of 

 the plant, especially, however, on the leaves and leafstalks. These 

 are small, more or less spherical bodies, with slightly depressed 

 ostiola ; pycnidia measure up to 200 1^ in diameter. The fungus 

 grows readily in artificial culture media, and it has been used by 

 Saida in some interesting experiments on the fixation of atmos- 

 pheric nitrogen. Frank states that the spores may remain alive in 

 moist soil throughout the winter without germinating, and then, 

 upon being placed in beet decoction, germination will promptly 

 proceed. 



Control. Spraying experiments have not yet given complete satis- 

 faction. Care should be taken to destroy such remains of the previous 

 crop as is practicable, and the treatment of seed with Bordeaux 

 mixture is desirable where disease abounds. Fortunately this fungus 

 has not made its appearance in this country up to the present time. 



XLII. DRY ROT OF SWEET POTATO 

 Phoma Batata Ell. & Hals. 



HALSTED, B. D. Some Fungous Diseases of the Sweet Potato. Dry Rot. 

 N. J. Agl. Exp. Sta. Built. 76: 23-25. fig. 16. 1890. 



This fungus is not uncommon in New Jersey, but it is not 

 to be considered one of the more serious enemies of the sweet 

 potato. A comparative study of this species and of forms upon 

 related hosts has not been made, and it is possible that it may be 

 referred to a species described earlier. It attacks the root, which 

 shows the effect of the invading organism only by a gradual shrivel- 

 ing and discoloration of the affected areas. The whole root may 

 become affected, and eventually dry and powdery. The pycnidia 

 appear upon the surface in large numbers, and the fungus spreads 

 rapidly during storage of the roots under moisture conditions. 

 The effects of this fungus are frequently complicated by those of 

 other organisms attacking the root, especially certain forms pro- 

 ducing soft decay. 



1 Bull. Sue. Myc. de France 7 : 15-19. 1891. 



