UROCYSTIS AGROPYRI ON REDTOP 



W. H. Davis 

 (With Text Figure i) 



On June 6, 1921, smutted plants of redtop, Agrostis palustris 

 Huds. (A. alba L.), were collected at Madison, Wisconsin, and 

 microscopic examination showed the smut to be Urocystis agropyri 

 (Pruss.) Schroet. 



The hosts and host ranges reported by Clinton in North Ameri- 

 can Flora 7 : 58. 1906 are as follows : Agropyron divergens Nees 

 {Agropyron spicatum (Pursh) Scribn. & Smith), Washington; 

 A. occidentale Scribn. {A. smithii Rydb.), New Mexico; A. repens 

 (L.) Beauv., Connecticut, Massachusetts and Vermont; Bromus 

 ciliatus L., Iowa; Bromus sp., Minnesota; Calamagrostis cana- 

 densis (Michx.) Beauv., Oregon; Elymus arenarius L., Green- 

 land; E. canadensis L., Illinois, Iowa, Kansas, Missouri, Nebraska 

 and Wisconsin; E. robustus Scribn. & Smith; E. virginicus L., 

 Illinois and Wisconsin; E. sp., Colorado and Minnesota. 



On redtop, the general appearance of the sori on the parts of 

 the plant is the same as described for other hosts. The pustules 

 form on the exposed culm, leaf sheath and blade, rhachis and 

 rhachilla and are especially numerous on the leaves near the top of 

 the culm. Striae, varying from 0.5 mm. in length to that of the 

 whole leaf, form between the leaf veins. When young, these striae 

 are raised and covered with light-colored, epidermal tissue of the 

 host which later ruptures forming a trough-like slit filled with the 

 spore balls. After the dispersal of the spore balls, the tissues 

 beneath the striae become transparent and finally the leaves are 

 shredded longitudinally. The culm above the sheath of the last 

 leaf is usually twisted and the black pustules either remain distinct 

 or coalesce on small areas of the culm. Although the plants when 

 -observed were only partially in blossom, many of the highly in- 



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