284 Bulletin 145. 



tical and scientific point of view in various publications of the U. S. 

 Department of Agriculture, and in many bulletins of the various Experi- 

 ment Stations. It will not be amiss further to emphasize the results 

 of general interest, especially in connection ^vith the notes already 

 given concerning the leaf-spot. The leaf-blight is well known wher- 

 ever the culture of the pear has been introduced, and since what is 

 probably the same fungus occurs abundantly on the quince and some 

 other members of the rose family, it finds abundant host plants for 

 fruitful propagation in almost any region. 



Ihe spots are very evident on the upper surface of affected leaves. 

 They occur at first as small discolored areas, becoming dull red with 

 darker margins. Singly, they are small with circular outlines ; but often 

 they are clustered together, or merged one into another. With age the 

 spots are darker, losing some of their characteristics. The leaf often 

 becomes yellowed or browned and is readily detached from the 

 branch by jarring. There may be seen in the center of each spot at 

 maturity a minute dark papilla. As noted later, it is herein that the 

 spores are borne. 



The spots of this fungus are usually smaller than those of the leaf- 

 spot, more nearly circular, and not so clearly defined on the under 

 surface. 



On the fruit the spots of the leaf-blight are red at first, but soon 

 become darker. The drying of the epidermal layers of cells may 

 cause a cracking of considerable extent, as in the case of pear scab, 

 an injury from which rotting may readily ensue. The term cracking 

 is no more to be applied to this disease, however, than to the scab. 

 Figure 166 shows a pear merely spotted by the disease. 



2. Microscopic Characters. 



Making a thin section through the spot of this leaf-blight where the 

 blackened papilla is noted, authors have described the spores as 

 massed just beneath the cuticle. These minute spores are very unique 

 in form, which to the imaginative mind of an early botanist suggested 

 a miniature insect well provided with feelers j hence the generic name 

 of the fungus, Entomosporium^ expresses this resemblance. See figure 

 167 for individual spores, 



