288 



Minnesota Plant Diseases. 



lion the mycelium rapidly drains away the nourishment which 

 should go to the heads and allows of an uncontrollable evapora- 

 tion of water through the broken skins; as a result the berries 

 do not fill but remain shriveled. Such wheat therefore, even if 

 not entirely ruined, suffers a loss of grade. 



FIG. 144. Cluster-cups of the crown rust of wheat (Puccinia coronata), on swollen cushions 

 of the stem of the alder-leaved buckthorn. Photograph by Arthur and Holway. 



It is also known that in states south of Minnesota the sum- 

 mer spores of grass rusts live through the winter and cause direct 

 infection of the grass plants in the spring. It is not impossible 

 that these spores from southern states can rapidly work their 

 way north in the early spring and commence the infection each 



