CLADOSPORIUM CITRI MASS. AND 

 C. ELEGANS PENZ. CONFUSED 



H. S. Fawcett 



A series of errors that need to be corrected appears to have 

 crept into plant disease Hterature, as to the name of the fungus 

 causing " scab " or " verrucosis " of Citrus. The first account 

 of this disease was pubHshed by F. Lamson-Scribner in October, 

 1886.* A fuller account with a colored plate appeared in the 

 annual report of the U. S. Commissioner of Agriculture for 1886 

 (pp. 120-121). Scribner referred to the fungus as Cladospor- 

 ium sp. A detailed account of the disease and the fungus was 

 later pubhshed by W. T. Swingle and H. J. Webber,"j" who also 

 referred to the fungus as Cladosporium sp. 



In Tubeuf and Smith's " Diseases of Plants," published in 1897, 

 reference is made on p. 509 to the above authors under the name 

 of Cladosporium elegans Penz. This is the beginning of the 

 errors. That the citrus scab referred to by Scribner is not 

 Cladosporium elegans is evident from Penzig's description and 

 figures in " Studi Botanici Sugli Agrumi," published in 1887. 

 The dimensions of the spores of C. elegans are too large and the 

 pathological effects on the leaf as figured by Penzig are not at all 

 the same as those described by Scribner. The spores of the 

 former are given as 18-20 X 5-6/^, while the latter are 8-9 X 

 2.5-4/x. 



Massee, in his Text-book of Plant Diseases," published in 

 1899, described both fungi. On p. 310, he describes the scab 

 under the name of Cladosporium Citri " protem," and says : 



This Cladosporium species is evidently quite distinct from 

 Cladosporium elegans Penz. which forms arid, brown spots on 

 living leaves of oranges in Italy." An error in print, however, 

 occurs on p. 436 of the same book, where a technical description 

 of the fungus is given under the heading 'Cladosporium Citri 



* Bull. Torrey Club 13: 181-183. 1886. 



t Bull. Div. Veg. Phys. & Path. 8: 20-24. 1896, 



245 



