4 MISC. PUBLICATIOX 1, U. R. DEPT. OF AGRICULTUKE 



You now know about three stages of the rust — the colorless stage 

 which i.s produced by the black stafre, the yellow cluster-cup stage 

 on barl)orry leaves iii the sprinjj:. and the red statre on wlieat (or 



FlC 2. — In tho sprluK thp rust forms uroiips of clustor cupH on t lie leaves of the 

 common I.nrlx'iry. TIk-si- rlii.st.T cups arf flllfd with thousanfls of spores wliuU 

 are carrlt-il by tlio wltids tu wheat and otlier grains or to grasses 



other prains or irras.ses) in the sunuuei". After the red staiie, there 

 comes a fourlli or black stage. 



As the <rrain bcLnns to ripen, pustules tilled with black spores 

 aj^pear. (Fig. 4.) Heoause of these lilack pustules the rust then is 

 called black stem rust, altliough it is the same rust. 



