164 ILLINOIS ACADEMY OF SCIENCE 



In the literature, the sooty blotch fungus as observed 

 on apple and pear fruits, is held to be morphologically 

 similar with the exception of Salmon and Wormald's 

 (1916) report. They state, after a description of sooty 

 blotch on apples, in England, that its appearance on 

 pears is very much the same, except that on apples there 

 are very numerous '^ minute black specks". It is very 

 likely that the sooty blotch, as Salmon and Wormald 

 observed it, was a comparatively^ young stage, since in 

 studying the trouble in Illinois on several varieties of 

 pears, it was noted that the very small black ''specks", 

 primordia of pycnidia, did not begin to appear until 

 October. This was about the same time that similar 

 ''specks" were forming on apples. 



Martin (1918) describes "Brown Blotch of the Kief- 

 fer Pear", which he believes is probably closely related 

 to the sooty blotch fung-us, but is disting-uished by its 

 smaller size, its straighter connecting strands, and that 

 it burrows into the cuticle, causing hypertrophy of the 

 subcuticular layers. It is clearly evident that the di- 

 sease Martin describes is not caused by the same fungus 

 the writer has treated in these pages. 



V. SUMMARY 



1. Sooty blotch is a common trouble of apples and 

 pears, of considerable economic importance, in North 

 America and England. 



2. It is entirely superficial, and does not cause rot or 

 bring about any perceptible host malformation. 



3. It was found on all varieties of apples examined, 

 when conditions were favorable for the fungus. 



4. Three thallus types have been observed, the fern- 

 like type (Fig. 7), the honey comb type (Fig. 11), and 

 the reticulate t^q^e (Fig. 12). 



5. Pycnidial development is commonly by the sympho- 

 genous method (Figs. 27-30). 



6. The fungus has been known as: 



Dothidea pomigena Schw. 



Asteronia pomigena (Schw.) fide Curt, in 

 Sprague. 



