THE AVHEAT SCAB 



199 



FIG. 82. 

 SPORES OF WHEAT 

 SCAB. MAGNIFIED. 



upper or lower half has prematurely whitened, leaving 

 the rest green, the wliitened part having on many of the 

 glomes a more or less distinct pink or orange covering 

 of the mycelium and spores of the fungus. Under a 

 high power of the microscope this 

 fungus is seen to be composed of long- 

 curved spores, as shown in Fig. 82. 

 According to the botanists, it is a 

 species of Fusisporium. The kernels 

 attacked by the fungus become mere 

 shells, covered inside and out with 

 mycelium (Fig. 83) and in passing- 

 through the thresher they are blown 

 away with the chaff. The yield is 

 sometimes greatly decreased. In 

 1890 I saw a field of one hundred 

 acres in Madison County, Ohio, con- 

 sidered the finest wheat field in the 

 county, which was expected, shortly before harvest, to 

 yield thirty-five to forty bushels per acre, so severely 

 attacked by the disease that the yield was reduced to 



eight bushels per acre. 

 Two other fields, one of 

 twenty-five and the other of 

 fifty acres, were shrunken 

 in yield at least one-third, 

 from the same cause. The 

 fungus apparently gains 

 access to the tender, unde- 

 veloped kernel, sapping its 

 life and sendino- down feed- 

 ers into the main axis of 

 the head on which tlie kernel and inclosing chaff are 

 borne. The functions of this part of the plant soon 

 become locally deranged, and, in consequence, the sup- 

 ply of nutriment for the portion of the head above the 



TIG. 83. 



WHEAT KERNELS AFFECT- 

 ED DY SCAT.. 



