Fusaria of Potatoes 121 



Appel and Wollenweber in 1910, and by Wollenweber in 1913), this 

 literature is usually not cited and a bibliography is omitted. 



The condition of the taxonomic literature on species of the genus 

 Fusarium in general is characterized by Wollenweber (1913 a: 41) as 

 presenting " an almost hopeless confusion." The only favorable exceptions 

 known to the writer are the works of Wollenweber, alone and in associa- 

 tion with other authors. These works are fully considered here. In 

 fact there is hardly any difficulty in recognizing Fusaria described by 

 Wollenweber. Nevertheless all available cultures of his organisms were 

 grown along with the other Fusaria, and a thorough comparison of living 

 material was made whenever it was necessary. 



When this work was actually completed there appeared the work of 

 Lewis (1913) on certain disease-producing species of Fusarium. The work 

 was supplemented also with Wollenweber's list of the names for the fungi 

 studied by Lewis, and also with certain remarks by Wollenweber in regard 

 to the taxonomy of those organisms. It appeared that certain of Lewis's 

 organisms were the same as those isolated by the writer from potatoes. 

 Cultures of four Fusaria, somewhat resembling certain species isolated 

 from potatoes, were obtained by the writer through the courtesy of Dr. 

 Morse, Plant Pathologist in the Maine Agricultural Experiment Station. 

 On comparison these four organisms — F. pirinum (Fries) Sacc, F. 

 conglutinans Wr., F. citrinum n. sp., and F. argillaceum (Fries) Sacc. — 

 were found to be distinct from all Fusaria presented here. 



SYSTEMATIC ARRANGEMENT OF THE SPECIES OF- FUSARIUM OF POTATOES 



The natural key to the species and their arrangement in sections, 36 as 

 given here, are in the main similar to those of Appel and Wollenweber 

 (1910:59-60) and of Wollenweber (1913 a: 28-32), respectively. Some 

 changes and additions have been made, however, in order to include 

 many new organisms. 



Variety is used as the smallest unit in the taxonomic treatment of these 

 fungi. An organism is classed as a variety if it differs from the closely 

 related species in only one character, even though the difference be con- 

 spicuous; the same treatment holds with respect to the organisms that 

 differ slightly in a few characters. When the differences are slight, but 

 in several important characters, the organisms are classed as distinct 



»The term is used by Wollenweber (1913 a: 28). 



