REED: SPECIALIZATION OF PARASITIC FUNGI 397 



their capacity for infection in the same way as uredospores from the 

 same gramineous hosts used as a source of the teleutospores for in- 

 fecting the barberry. The only marked variation from this is in the 

 case of aecidiospores from the barberry produced by inoculation with 

 teleutospores from Bromus madritensis, Briza maxima, Festuca myurus, 

 and Phalaris canariensis, all hosts for the race Avenae, which infected 

 not only Avena sativa but also Secale cereale, a host of race Secalis of 

 the rust. 



Jaczewski (68) found close correspondence in the infecting capacity 

 of aecidiospores from the barberry arising from teleutospore inocu- 

 lations from definite plants and that of the uredospores from the same 

 gramineous hosts. In fact his establishment of the nine specialized 

 races of the black stem rust in Russia is based as much on aecidiospore 

 inoculations as on uredospore inoculations. 



Stakman (143) also found no essential differences in the infecting 

 capacity of uredospores from wheat and Agropyron repens and that of 

 aecidiospores from the barberry arising as a result of inoculation with 

 teleutospores from these same hosts. Pritchard (no) also found a 

 correspondence between the infecting capacity of uredospores and 

 aecidiospores. 



Bolley and Pritchard (20) assert that aecidiospores from a single 

 barberry hedge have been used to infect wheat, oats, barley, Hordeum 

 jubatum, Agropyron tenerum and A. repens. The origin of the infec- 

 tion of the barberry was not known but probably was due to teleuto- 

 spores from Hordeum jubatum. In 1905 aecidiospores from barberry 

 readily infected barley and Hordeum jubatum, less readily wheat, and 

 oats hardly at all. 



Arthur (10), however, has come to the conclusion that the "bar- 

 berry acts as a bridging host between each and every other gramineous 

 host." The evidence that he gives in support of his statement may 

 be indicated: (i) aecidiospores from barberry, produced by inocula- 

 tion with teleutospores from Agrostis alba, infected wheat and barley, 

 but not oats; (2) aecidiospores from barberry produced by inocula- 

 tion with teleutospores from Agropyron tenerum, infected oats; (3) 

 aecidiospores from the barberry, produced by inoculation with teleuto- 

 spores from Sitanion longifolium, infected wheat; (4) aecidiospores 

 from the barberry, produced by inoculation with teleutospores from 

 Elymus canadensis, failed to infect wheat and rye. No one has 

 recorded any data on the infecting capacity of uredospores developed 

 on Sitanion longifolium; accordingly we have no information whether 

 this rust is a distinct race or whether S. longifolium is merely a host 

 for specialized race Tritici. Further, Agropyron tenerum is a host for 

 specialized race Avenae; hence the results recorded are just what one 



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