SPECIES OF CLAVICEPS 195 



ent 1 week after the first appearance of honey dew, whereas in 

 dry weather 2 weeks may elapse. Sclerotial formation progresses 

 gradually, and the sclerotia normally reach maturity by the time 

 the rye is ready to be harvested. 



Ordinarily young ovarian tissues are completely destroyed and 

 are replaced by the sphacelial mycelium. Sometimes, however, 

 the upper portion of the ovary remains. At any rate, a rather 

 densely interwoven mass of hyphae replaces the normal grain, 

 which it exceeds by several times in bulk. These hyphae become 

 densely compacted at the exterior of the mass, forming the scle- 

 rotium. These sclerotia are yellowish brown and cartilaginous 

 when they first attain their mature size, but on drying they be- 

 come grayish violet and are corneous. 



Hosts. Claviceps piirptirea is world-wide in distribution and 

 occurs on approximately 200 species and varieties of grasses, a 

 list of which appears in the monograph of Barger (1931, pp. 117- 

 122). In w^et seasons it causes an important disease of r^^e but is 

 of less consequence on wheat, oats, and barley. Cases are on 

 record in which 20 to S0°/o of rye heads have been ergotized. 

 More commonly the losses in yield of rye are less than 1%. 



The injury to forage grasses is greater than that to cereals. 

 Single heads of Agropyron Occident ale are known to produce 40 

 ergot grains, 5 or 6% by weight of the seed being ergot. Rostrup 

 [Atanasoff (1920), p. 5] found 2700 sclerotia in a sample pound 

 of Festuca seed, 5600 in one of Poa, 500 in one of Holcus, and 

 2500 in one and 2700 in another of two samples of Agrostis alba 

 seed. 



Species of Claviceps. Of the 20 named species of Claviceps, 

 8 are indigenous to Europe, and 12 to America. Those recorded 

 for Australia appear to have been introduced into that continent. 

 Undoubtedly unnamed species occur in Asia and Africa. Species 

 are separated on the bases of shape, size, color and dimensions of 

 stromata, and dimensions of perithecia, asci, ascospores, and co- 

 nidia. Paraphyses are present in some species but lacking in 

 others. 



These morphological characteristics, although useful in spe- 

 cific identification, may not always be sufficient criteria. This 

 appears to be the situation ^^'hen Claviceps paspali and C. rolfsii 

 must be distinguished, the reported dimensions of the former be- 



