1891.] PUBLIC DOCUMENT — No. 33. 203 



C. H. Peck, New York State Botanist, gave the first cor- 

 rect account * of some details of the structure of Sphceria 

 morbosa, then first describing the summer spores and the 

 time of maturity of the winter spores. In 1875 Dr. Thos. 

 Taylor gave f an illustrated account of the fungus, which 

 was incomplete and incorrect in several particulars, and 

 added nothing to previous knowledge. 



Now followed the fullest and best account we have of 

 the structure and life historv of this fungus, which was 



■J o ' 



held to be the sole cause of black knot. It was by Dr. 

 W. G. Farlow % of Harvard University, and remains the 

 authoritative account of the disease and its cause, to-day. 

 The author described the summer and winter spores, and, 

 as will be noticed later, other secondary forms, and figured 

 the various organs. This paper has served as the basis of 

 the present, as it must of all work on the black knot ; but 

 its comparative inaccessibility renders the repetition of cer- 

 tain descriptions and illustrations not superfluous in connec- 

 tion with the new facts to be presented here. Since its 

 publication, the authority of this paper as to the cause of 

 the disease has remained unquestioned, and all conflicting 

 theories have fallen into discredit among scientific students 

 and observers. 



The black knot is known to attack nearly all our wild 

 or cultivated species of plums and cherries ; but, so far 

 as the cultivated fruits are concerned, the plums are by far 

 the greater sufferers. It has been thought there must be 

 two or more species of fungi which produce the knots on 

 different host-species. Walsh, for instance, considered that 

 there are two fungi, one attacking the plum and the other 

 the cherry ; and a reviewer of his paper suggested a third 

 on a species of wild plum. Others have based arguments 

 for this opinion chiefly on the fact that certain hosts some- 

 times suffer from epidemics of the black knot, while others, 

 equally liable to its attacks, remain free.§ De Schweinitz 



* A Paper on Botan.v, read as a Report before Albany Inst., Feb. 6, 1872. 

 t Monthly Micros. Journal, Vol. XIII, p. 118, with two plates ; London, March, 

 1875. 

 X Bulletin Bussey Institution, Part V, p. 440, with three plates (1876). 

 § See Gardener's Monthly, November, 1866, p. 335. 



