646 THE FUNGI WHICH CAUSE PLANT DISEASE 



Fusarium Link (p. 645) 



Sporodochium pulvinate, or subeffused; conidiophores branched; 

 conidia terminal, solitary, fusiform or falcate, more or less curved, 

 pluriseptate. 



In part=Nectria, Neocosmospora, Gibberella. See pp. 201, 

 205, 206. 



This is a large genus, (some four hundred species have been de- 

 scribed) though future study will undoubtedly relegate many 

 names to synonymy. 



Many of the species are destructive parasites, invading the ducts 

 of plants and by stoppage of the water-supply causing the class of 

 diseases known as "wilts." Others induce rot, spotting, cankers, 

 etc. Taken as a whole the genus is one of the most injurious with 

 which plant pathology has to do. 



It seems probable that some of the forms that live normally as 

 saprophytes in soil may encroach upon living roots of susceptible 

 plants when these are available. 



In nature the spores typical of this form-genus are borne in 

 sporodochia, coremia or acervuli and are crescent-shaped or fusoid. 

 The same mycelium that produces these structures often, indeed 

 usually, produces also similar and smaller conidia scattered 

 on single hyphse (=Cephalosporium). These two foi-ms are called 

 macroconidia and microconidia respectively. The microconidia 

 are regarded by Appel & Wollenweber '** as depauperate mac- 

 roconidia. Frequently chlamydospores form in the mycelium; 

 either terminal or intercalary. Sclerotia are also not uncom- 

 mon. 



Undoubted species of Fusarium have been shown to belong to 

 several different Hypocrealous ascomycetes, while still more have 

 as yet revealed no ascomycete connection. 



Biologic specialization has been found, in that forms morpho- 

 logically indistinguishable are frequently incapable of cross in- 

 oculation onto other than their usual hosts. 



Fusarium grows well in culture and the species often show- 

 marked differences in growth on various media, particularly in 

 the colors that are developed. 



As with the anthracnoses much study is here needed to throw 



