TWENTIETH Annual Meeting. 15 



If they are a result in any sense, they are a necessary result; because they occur 

 invariably. 



Not a single specimen of the black rot in any stage has ever been placed under a 

 microscope without revealing the presence of the characteristic fungus, distinctly 

 correlated to the stage of decay found in the specimen. If the fungus was only a 

 possible result, specimens would inevitably be found among the thousands exam- 

 ined, in which the fungus was absent. If it is not a result, it must be a cause. 



It is a cause. 



It is the exciting cause, and no matter how much the vine may be predisposed 

 to the disease, without the action of the exciting cause the rot will not take place. 



The history of the advent of the disease into France is of itself sufficient to prove 

 that some peculiar and special condition is necessary as an exciting cause to pro- 

 duce the rot. 



For hundreds of years France had been one of the greatest vine-growing coun- 

 tries in the world. She had furnished fruit for every market in the world, and her 

 wines were to be found in every city in the world. The vineyards of France were a 

 national pride. The vines were tended, pruned, trellised, and fertilized with the great- 

 est care. Diseases of many kinds showed themselves, but were nearly always con- 

 trolled by ordinary :neasures; and never was the black rot known in France until 

 the year 1885, two years previous to the present writing. 



The same treatment of the vines has been pursued since; the same method of 

 pruning, trellising and fertilizing has been used, but the spirit of Death stalks on 

 through the luxuriant vineyards, touching with his deadly finger berry after berry, 

 cluster after cluster, and they die. 



The fruit forms and grows beautifully up to a certain size, giving promise of a 

 magnificent yield. No prospect could be finer. Suddenly a minute spot appears 

 here and there upon the surface of a berry; a whitish or yellowish spot which may 

 be elevated like a blister on the human skin. Rapidly a dark areola forms around 

 it; then a system of concentric dark rings with lighter spaces between which grad- 

 ually give way to the uniform dark-brown color of the disease. Other spots appear 

 and pursue a like course; then others, and still others; all enlarging rapidly until, 

 in an amazingly short space of time, the entire vineyard is studded with rapidly 

 darkening berries. Whole bunches are blighted; but each individual berry is made 

 the object of a separate attack. Not a leaf, not a stem, not a petiole is affected 

 primarily; only the beautifully clustering fruit which looked so fair, and promised 

 so fairly. 



It, is a striking phenomenon, and one which almost unconsciously prompts the 

 question: "What can be the cause of all this untimely death and decay?" 



Not until the searching eye of the microscope was turned upon the object of our 

 study were we able to answer satisfactorily this question. It would seem that the 

 seeds of death had been sown broadcast by an invisible hand; and, indeed, this is 

 about what occurs, as we shall see. 



As early as 1861 the p/iowia uvicola was observed and described by Dr. Englemann, 

 but its natural history is so complex that all the years intervening between that time 

 and the present have contributed very little to our knowledge of it, until the last few 

 years, when Viala and Ravaz, Scribner, Trelease and others have again taken up the 

 subject. 



At any time after the whitish spot has declared the presence of the disease in the 

 berry, a cross-section through the affected portion will show the threadlike hyphae 

 of a mycelium burrowing between and through the cells of the grape tissue. In the 

 early stage of the disease the growth of the mycelium is confined to the tissue un- 

 derlying the epidermis, but as the disease progresses it encroaches more and more 



