WHEAT CPLTURE. 



343 



produces little brown tufts on the stem and leaves (Fig. 11). which arc 

 found to consist mainly of spores upon short stalks; sometimes these spores 

 are one-celled uredospores (summer spores) sometimes thej are two-celled 

 teleutospores I Fig. 12). 



The one-celled uredospores are produced throughout the season in 

 immense numbers. They are very minute and light, and arc easily distri- 

 buted by the wind. They aid in carrying over the Rus1 from year to year by 

 infecting self-sown wheat on beadlands, and they are frequently to be found 

 caught in the lf brush" of wheat grains (see Fig; :;. Hunt spores). 



Fig. 11.— Rust. Cross section of a small piece of Wheat Stem. 

 Showing patches (sori) of the two-celled spores (teleutospores) of Puecinia graminis. 



The two-celled teleutospores are produced towards the end of the season. 

 They will not germinate immediately, but only after a period of rest. 

 The teleutospores of the Wheat Rust of Europe are capable of infecting the 

 small barberry shrub, and when they ■!" so a third kind of spore is pro- 

 duced. In Australia barberry shrubs have only been introduced in a \'<'\\- 

 places, and are nol at all common. It has recently been shewn by -Mr. \V. L. 

 Waterhouse that the teleutospores of the Australian Rust, Puecinia 

 <i rami his, can hi' used to artificially infect the barberry. It seems that this 



