1 62 DISEASES OF CULTIVATED PLANTS 



Notwithstanding the serious injury caused by the fungus in 

 seed beds and fields, but little is known respecting preventive 

 measures. It is proved that the fungus is most aggressive in 

 soil containing stagnant water, which suggests the necessity of 

 better drainage. Professor Clinton recommends sterilising 

 the soil of seed beds with a pint of commercial formalin 

 mixed with twelve and a half gallons of water, using two- 

 thirds of a gallon to each square foot. The soil should be 

 covered with sacking for two days to keep in the fumes of 

 the formalin. Commercial fertilisers may be applied either 

 before or after the bed is treated, but manure should be used 

 before treatment, so that it may be sterilised. A week at 

 least should elapse after treatment before the sowing or 

 planting is commenced. 



Berkeley and Broome, Ann. Mag. Nat. Hist., Ser. 2, v. 

 p. 461 (1850). 



Zopf, Sitz. Bot. Ver. Prov. Brandenburg^ 18, p. 101 (1876). 



Zopf, Zeit. Pflanzenkrankh.) i, p. 72 (1891). 



Clinton, Connecticut State Agric. Exp. Sta. Rep., 1906, 

 p. 342. 



DIMEROSPORIUM (FCKL.) 



Perithecia depressed, membranaceo-carbonaceous; asci sub- 

 globose, 8-spored ; spores i -septate, hyaline or brownish ; 

 mycelium abundant, black, forming a film, often bearing 

 conidia. 



Mango black blight (Dimerosporium mangiferum, Sacc. 

 = Capnodium mangiferum, Cooke and Broome) forms 

 intensely black, velvety patches on both surfaces of the leaves 

 of the mango (Mangifera indicd). The fungus commences as 

 little black points which extend rapidly and encroach on each 

 other, so that eventually the greater portion, or even the 

 whole of the leaf surface, is covered with a dense weft of 

 mycelium. This felt is generally easily rubbed off by the 

 fingers, and does not enter into the tissues of the leaf, never- 

 theless it is very injurious, as its presence prevents the leaf 

 from performing its normal functions. It is suspected that 

 the present fungus, like many of its black, film-forming allies, 

 is favoured by the presence of ' honey-dew ' on the leaves, 

 deposited by aphides, etc. Under the circumstances the 



