20 Robert S. Kirby 



occurs as a plate-like mass. It causes a discoloration of the first and 

 second internodes, forming a dark brown or black zone at the base of the 

 diseased culms. Perithecia are formed during Juno and .Inly in com- 

 paratively large numbers on the stems and in small numbers on the roots. 

 After the death of diseased plants, or rarely before, the beaks of the 

 perithecia may protrude through the outer leaf sheath. 



In rye the plate mycelium is less pronounced and fewer perithecia are 

 developed than in wheat, while on the susceptible wild grasses a definite 

 plate-mycelium is practically always lacking. 



Comparative symptomatology 



True take-all differs in its signs and symptoms from the so-called 

 " take-all " of Humphrey, Johnson, and McKinney (1921) reported 

 from Madison County, Illinois, in that the latter disease exhibits hyper- 

 plastic instead of hypoplastic symptoms, there being an excessive pro- 

 duction of culms in the Illinois disease; moreover, perithecia are wanting. 

 Take-all differs also from the European foot-rots, the causes of which 

 are usually not given by most investigators, though variously attributed 

 to one or more of the following fungi: Ophiobolus herpotrichus, Leptos- 

 phaeria herpotrichoides, L. culmifraga, and Fiisarium sp. Dr. D. 

 Atanasoff states 5 that the European foot-rot is connected with a pathologic 

 condition of the cereals which has nothing in common with the Australian 

 or the American take-all. The European foot-rots are characterized by a 

 wilting, breaking, and bending-over of fully grown plants, usually single 

 plants or culms that have rotted bases. He says that affected plants 

 are usually uniformly scattered throughout the field. Foex (1919 b) 

 differentiates between the symptoms of take-all and the Leptosphaeria 

 foot-rot, which is more characteristic of the European type of foot-rot, 

 in that the take-all pathogene attacks the base of the stem and the under- 

 ground parts, causing atrophy and premature dying, while Leptosphaeria 

 herpotrichoides causes lodging and produces fruiting bodies higher up the 

 stem. 



ETIOLOGY 



Nomenclature 



The causal organism of the disease is Ophiobolus cariceti (B. & Br.) 

 Sacc. In a previous paper (Fitzpatrick, Thomas, and Kirby, 1922) the 

 evidence indicating that Ophiobolus graminis Sacc. and Sphaeria cariceti 

 B. & Br. are the same organism has been presented. 



Pathogenicity 



Attempts to prove the pathogenicity of the fungus are reported by 

 Delacroix (1901), Mangin (1902), and McAlpine (1904), each of whom 



» In a tetter to the writer dated March 9, 1923. 



