xx Minnesota Plant Diseases. 



FIG. 137. Poplar leaf rust. Original 278 



FIG. 138. Willow leaf rust. Original 280 



FIG. 139. Wheat rust. Stems of wheat, showing opened and unopened 



black clusters of winter spores. Slightly magnified. 



Original 283 



FIG. 140. Wheat rust. A section of such a stem as is shown in Fig. 139, 



highly magnified. Microphotograph by E. W. D. Holway 284 

 FIG. 141. Oat stems and leaf bases, with clusters of summer spores of 



the oat rust. Original 285 



FIG. 142. Spores of the common "black rust" of wheat. After Arthur 



and Holway 286 



FIG. 143. Spores of the crown rust of wheat. Highly magnified. After 



Arthur and Holway 287 



FIG. 144. Cluster-cups of the crown rust of wheat, on swollen cushions 



of the stem of the alder-leaved buckthorn. Photograph by 



Arthur and Holway 288 



FIG. 145. Cluster-cups of the black or stem rust of wheat, on stems and 



leaves of the barberry. Photograph by Arthur and Hol- 

 way 290 



FIG. 146. Loose smut of oats. Original 293 



FIG. 147. Stinking smut of wheat, showing smutted grains and spores. 



Variously magnified. After Tubeuf 296 



FIG. 148. Smut of corn. On the leaves and tassels. After Clinton. .. . 298 



FIG. 149. Corn smut on an ear of corn. Original 299 



FIG. 150. Head smut of sorghum. After Kellerman 301 



FIG. 151. Grain smut of sorghum. After Kellerman 302 



FIG. 152. Powdery mildew of grasses on wild grass-plant leaves. 



Original 304 



FIG. 153. "Black mold" of clover on leaves of white clover. Original 305 



FIG. 154. The ergot fungus on rye. After Clinton 307 



FIG. 155. Storage organs or ergots of ergot fungi on various grasses. 



Original 308 



