48 THE KUSTS OF GRAINS IN THE UNITED STATES. 



and prevalence of red rust, Puccinia rubigo-vera, is attributed in part 

 to the ability of that species to winter its mycelium" (21, p. 14). 

 Apparently the same instance is cited by' him in a later publication 

 (22, p. 107). 



The same author in 1891 (23, p. 260) says: 



The red rust (uredo of P. rubigo-vera and P. coronata) is developed to a greater or 

 less extent during all months of the year in States south of Tennessee. * * * In 

 the States north of this line there seem to be isolated cases in which the mycelium 

 may persist through winter, dependent, apparently, chiefly upon the point whether 

 the attacked portion of the host persists or not. 



Hitchcock and Carleton (57, p. 11; 29, p. 453) found in Kansas 

 throughout the winter months (January 23-25, February 25, and 

 March 1) viable uredospores of Puccinia rubigo-vera on wheat. They 

 state: 



It would seem that the uredospores were not formed during the winter, but had 

 retained their vitality since the preceding fall. 1 



Again, Bolley (24, p. 894) says that fresh uredospores of Puccinia 

 rubigo-vera can be found in the United States throughout the whiter 

 in States south of Ohio, and although new spores are not formed in 

 States as far north as Indiana and Kansas during the coldest periods, 

 those already formed retain their viability. 



Carleton (30, p. 21), in speaking of the uredo of Puccinia rubigo- 

 vera on wheat, says that the conclusions of Bolley, Hitchcock, and 

 Carleton as to the wintering of the uredo have been confirmed and 

 reconfirmed by him both in Kansas and in Mar}dand. 



In the Southern States the leaf rusts of both wheat and rye not only live but grow all 

 winter. * * * In latitudes below 40° in this country, leaf rust of wheat is able to 

 pass a perpetual existence in the uredo stage on wheat alone, without intervention of 

 any other stage. 



Again he maintains (30, p. 44) that Puccinia rubigo-vera secalis 

 lives over winter in a similar manner, and it is his opinion that this 

 rust ''readily passes the winter as a uredo in all parts of the United 

 States." He found the uredo in great abundance in a patch of 

 volunteer rye at Lincoln, Nebr., in November, 1897, and afterwards 

 in midwinter in the same place. April 15, 1898 — 



it was still present in considerable quantity, but was confined entirely to the leaves 

 of the previous autumn's growth and had without question lived through the winter, 

 though the leaves were still somewhat green. 



Some of the uredospores germinated in water-drop cultures. Two 

 days later the uredo was found in considerable quantity several 

 miles from this locality. 



In neither case was there any production of new spores, and yet the spring was so 

 far advanced that there could be no question about the continual growth of the rust. 



J The minimum temperatures (F.) at this time were: For December, —9°; January, —1°; February, —6°. 

 216 



