158 MISSOURI STATE HORTICULTURAL SOCIETY. 



No doubt many of you arc aware that this plant belongs to a group 

 whose members are known as parasitic fungi ; these attack the higher 

 plants, break clown their tissues and use the material obtained in this 

 process, in building up their own bodies. The parasite in question pos- 

 sesses characters, by which it is distinguished from similar species, as 

 those possessed by the grape upon which it feeds. These facts will en- 

 able you to understand that you are really fighting something tangible, 

 when you undertake combating the black-rot fungus, and they also re- 

 veal to you the importance of knowing thoroughly the life history of 

 these minute plants before making any attempt to prevent their rav- 



ages. 



EXTERNAL AND BOTANICAL CHARACTERS OF THE FUNGUS. 



The parasite attacks the young branches, the leaves, and their sup- 

 porting stalks, the fruit, and occasionally the stems which support the 

 latter. Upon the leaves the fungus produces reddish brown irregularly 

 shaped spots which frequently coalesce or run together and form large 

 blotches. In Missouri the spots usually appear about the last week in 

 May or the first week in June, which is at least ten or fifteen days be- 

 fore the berries reveal the presence of the fungus. The young branches 

 are attacked about the same time that the leaves begin to show the ef- 

 fects of the malady ; but here the spots are black or dark brown and are 

 usually elongated in the direction of the stride of the bark. The effects, 

 produced by the fungus on the fruit, are so well known that only a pass- 

 ing notice is necessary. Generally there first appears a browr ish spot 

 upon the berry, this rapidly increases in size and soon becomes black 

 at the same time the fruit begins to shrivel and soon dries up entitely. 

 Close examination of the berries at this stage of the disease reveals 

 numerous black postules scattered irregularly over the surface. Similar 

 postules are also found on the diseased leaves and branches, but in the 

 latter instance they are more distinct and are usually arranged in more 

 or less definite circles. 



The external characters above described are due to the development 

 of the body of the parasite — which is known as mycelium — within the 

 tissues of the leaves, branches and fruit. The mycelium consists 

 of very slender, much branched, colorless, septata filaments ; these 

 traverse the tissues both between and through the cells and under their 

 action the latter lose their shape and their contents turn brown (Viala 

 and Ravaz, " Le Black Rot," p. i8). In the process of growth the my- 

 celium gives rise to numerous rounded bodies which are at first colorless 



