18 



INVESTIGATIONS OF RUSTS. 



hosts. a The results of the culture experiments are given in the follow- 

 in o- table: 



Table III. — Culture experiments with black stem rust of Agrostis alba vulgaris. 



Date. 



Locality. 



0rigin material Ulating Plant in °culated. 



Period 

 of incu- 

 bation 

 in days. 



Result. 



Dec. 23, 1897... 

 Do 



Lincoln, Xebr 



do 



Agrostis alba vulgaris. Agrostis alba vulgaris. 



8 

 8 

 8 

 12 

 12 

 14 



Success. 



Do... 



.do.. 





Do. 



Jan. 24, 1898... 



...do... 





Do. 



Do 



do 



do 



Oats 



Do. 



Feb. 11, 1898... 



do 



Elymus canadensis 

 glaucifolius. 



Agrostis alba vulgaris. 



Do. 



The rust is evidently of the black stem rust group (Puccinia graminis 

 of authors), but contains quite a number of abnormal teleutospores, 

 including mesospores. Many measurements of these spores average 

 27-54 by 16-23yu, mostly 40-46 by 16-18/*. 



Rust of Chloris {Puccinia cJiloridis Diet.). 



The uredoform of this rust is sometimes very abundant on Chloris 

 verticillata in the Great Plains region, occurring in late summer and 

 autumn. The sori are deep brown in color. The uredospores germi- 

 nate very freely and easily. In a number of experiments made in 

 1898 it was found that the uredo on C. verticillata and C. elegans 

 would readily transfer from either host to the other, but not to other 

 grasses, in several cases which were attempted. In a watch-glass cul- 

 ture, made March 18, 1898, of uredospores from C. elegans, produced 

 from artificial infection in a greenhouse, not only these spores germi- 

 nated freely, but a number of newly formed teleutospores at the same 

 time, an occurrence unusual except in the Lepto-uredineae. Among 

 thousands of cultures made by the writer only one other instance of 

 this kind has occurred. In the summer of 1895 at the Biological Lab- 

 oratory at Cold Spring Harbor, Long Island, both teleutospores and 

 uredospores taken from the same sorus of a rust on Luzula campestris 

 gave good germinations. 6 



Rusts of Willow and Cottonwood (Melampsora). 



Both the uredospores and teleutospores of the rusts of willow and 

 cottonwood germinate readily, the germ tubes of the latter containing 

 always brilliant endochrome. Healthy leaves of either cottonwood or 

 willow placed in a damp chamber have often been infected by the 



a Arthur describes culture experiments made by his assistant, William Stuart, in 

 July, 1898, in which wheat plants were infected with uredospores from this host, 

 but the spores of the infection sori were larger than those of the original material. 

 (Bui. Lab. Nat. Hist, State Univ. Iowa, vol. 4, No. 4, pp. 396-397, 1898.) 



&The species was, without much doubt, Puccinia obscura Schroet. 



