44 CEREAL RUSTS OF THE UNITED STATES. 



The period of incubation for the orange leaf rust of rye is apparently 

 a little longer than for the orange leaf rust of wheat, ranging from 

 eight to twelve days with ordinary greenhouse conditions. In a few 

 cases where, as the table shows, this period was extremely long, time 

 was allowed for the rust to infect other plants if it would, the rye itself 

 having become infected at a much earlier date. 



The experiments thus far made show that orange leaf rust of rye may 

 occur in this country on cultivated varieties of Secede cereale and on S. 

 montanum. It was actually found on the latter host at Lincoln, jSTebr., 

 November 16, 1897. 



Occurrence and distribution. — As previously stated, this rust is always 

 present where rye is grown, but its distribution is limited in this coun- 

 try because rye is not extensively grown here. Like the corresponding 

 rust of wheat, it seems to be more abundant in the Southern States. 

 According to Humphrey (40, pp. 228, 229) and Thaxter (67, p. 98), it 

 also occurs in considerable abundance in Massachusetts and Connecti- 

 cut. What is said of its distribution in this country is true of it also 

 in foreign countries, except in Eussia and Germany, where rye is gTown 

 to a great extent, and where it is probably a much more prominent 

 rust. 



Winteri7ig of the uredo. — In the Southern States this rust, like the 



leaf rust of wheat, not only lives over, but propagates through the 



winter in the uredo stage. As rye is rather hardy, the writer's opinion 



is that the rust readily passes the winter as a uredo in all parts of the 



United States, but owing to the small extent to which the crop is grown 



he has not been able until very recently to demonstrate its ability to do 



so in any locality, and Humphrey (40, p. 229) failed to find any evidence 



that it does so in Massachusetts. However, in November, 1897, the 



writer found the uredo in great abundance in a patch of volunteer rye 



at Lincoln, Nebr., and afterwards, in midwinter, it was seen in the 



same place on green leaves. On 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 placed in water-drop cultures germinated, a few of them 



producing very long germ tubes. Two days afterwards, that is, April 



17, the uredo was again found in considerable quantity several miles 



from the other locality in a large field of rye seeded for pasturage, 



being, as before, confined entirely to the leaves of the previous autumn's 



growth. 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 continued growth of the rust. The weather was unusually 



cold in November and December, the temperature falling to — 27| C. 



on the 18th of the latter month at the State University, but ou the 



whole the winter was not particularly severe. 



The uredo of this rust probably winters over in most other countries 

 also, but in nearly all observations so far made by others concerning 



