FUNGI IMPERFECTI (dEUTEROMYCETES) 



267 



fungus which causes leaf spot of beets, Cercospora beticola. The form 

 genus Fusarium (Fig. 109), established by Link in 1809, is one which 

 has come into prominence recently as associated with the production 

 of serious plant diseases. At least eleven species are found on the 

 sweet potato (Fig. 108), and these have been investigated by H. W. 

 WoUenweber' and other mycologists. He finds that the genus has a 

 number of vegetative and spore stages the variability of which has 

 caused confusion, as transfers of myceUum produce a growth quite 

 different in general appearance from that derived from spores from the 



Fig. 109. — Spores of two stem-rot organisms. A, Fusarium hataialis and B. 

 F. hyperoxysporum, XSOO. {After Barter, L. L., V. S. Farmers' Bull. 714, March 11, 

 1916.) 



same medium under conditions otherwise identic. 'JVoUenweber and 

 AppeP have published a monograph of Fusarium and later Wollen- 

 weber has studied the Fusarium problem and similar studies should 

 be made of each one of the form genera of the Fungi Imperfecti. 

 The genus Fusarium is divisible into sections not only by physiologic 

 characters (pathogenicity) but also by morphologic characters (coni- 

 diospores, chlamydospores). The section, Elegans, comprises the 

 vascular parasitic Fusaria, which are serious enemies of plants, causing 



' WoLLENWEBER, H. W. : Identification of Species of Fusarium occurring on 

 the Sweet Potato, Ipomcea batatis. Journal of Agricultural Research, II: 251-286 

 July IS, 1914- 



^ Appel, Otto, and Wollenweber, H. W. : Grundlage einer Monograph 

 der Gattung Fusarium Link Arb. Biol. Anst. f. Land. u. Forst., Bd. 8, Heft. 1, 

 pp. 1-207; Phytopathology III: 24-50. 



