46 THE RUSTS OF GRAINS IN THE UNITED STATES. 



Germany. He considers the wintering of the uredo of P. dispersa 

 (P. rubigo-vera) and of P. glumarum to be possible. 1 



Denmark. — According to Eriksson and Henning (39, p. 38), 

 Kostrup (87, p. 55) considered the wintering of the uredo of Puccinia 

 graminis very possible in mild winters in Denmark, especially as it 

 sometimes appears before the secidiiim on the barberry. 



Sweden. — Eriksson and Henning (39, pp. 40, 41, 131) were unable 

 to find that Puccinia on Agropyron repens, Dactylis glomerata, and 

 Agrostis vulgare winters over in the uredo stage in Stockholm. They 

 were inclined to believe, however, that Puccinia phlei-pratensis winters 

 in the uredo. 



In a letter from Eriksson to the authors dated December 28, 1907, 

 he states that his conclusions as to the wintering of the uredo of 

 Puccinia phlei-pratensis published in Die Getreideroste, 1906, lack 

 sufficient support; that conditions are very probably the same for 

 this rust as for the cereal rusts — i. e., it does not winter in the uredo 

 stage. 



The wintering of the uredo of Puccinia dispersa, either as spore or 

 mycelium, according to Eriksson and Henning, does not take place 

 in Sweden (39, p. 218), and according to these authors the probabil- 

 ity of the uredospore of P. glumarum, the yellow rust common in 

 Scandinavia, England, and India, living over winter is \ery slight, 

 at least in the vicinity of Stockholm. 



England. — Plowright (85, p. 234) found uredospores in England on 

 Agropyron repens in December, 1881, and again in March; whether 

 Puccinia graminis or P. rubigo-vera is not absolutely clear. He adds: 



This spring our Norfolk and Suffolk wheats were much affected with rust; some of 

 this may be and probably was due to the Uredo linearis kept alive from the previous 

 autumn, but the bulk of it was due to the uredo of Puccinia straminis (P. rubigo-vera), 

 which is always an earlier uredo than that of P. graminis. 



The same author (84, p. 35) affirms that the uredo of Puccinia 

 rubigo-vera can be found throughout the whole winter in England. 

 Ward (99, p. 132) found viable uredospores of P. dispersa on Bromus 

 during every month in the year. 



Biffen (17, pp. 241-253) believes that the yellow rust Puccinia 

 glumarum also winters in the uredo stage in England. He says: 



The uredospore stage seems to be sufficient to enable the fungus to tide itself over 

 the winter, for it is possible to find pustules of rust on the foliage of self-sown wheat 



1 In an article which has appeared while this paper was in preparation Hecke (Natnrwissenschaftliche 

 Zeitschrift fur Forst- una Landwirtschaft, vol. 9, pt. 1, Jan., 1911, pp. 44-53) brings forth experimental 

 evidence to showthat the uredo mycelium of yellow rust, Puccinia glumarum, winters over in the leavesof 

 the winter grains at Vienna, Austria. He inoculated winter wheats in pots October 28 and November 21, 

 1909, left them in the greenhouse for three days, and brought them into the open, where they remained all 

 winter. Pustules of yellow rust appeared March 28, 1911, on the- inoculated leaves, while control leaves 

 remained rust free. In this instance the incubation period of this rust must have been four and five 

 months, during which time the mycelium remained practically dormant. 

 216 



