162 ILLINOIS ACADEMY OF SCIENCE 



IV. GENEKAL DlSCUSSIOISr 



It lias been shown that the names sooty blotch and fly 

 speck have been confounded, and some authors have held 

 that the two are but different forms of the same fungus. 

 The morphological studies so far carried on by the writer, 

 however, do not enable him to regard the sooty blotch 

 and fly speck as caused by the same fungi, for the fol- 

 lowing reasons : 



On many apples, collected at various times of the year, 

 from Illinois and other states, shoAving a large amount 

 of soot}^ blotch, no fly speck was present (Frontispiece). 



It has often been observed, that where colonies or thalli 

 of the fly speck and sooty blotch fungi approach each 

 other, one of these fungi exerts an inhibiting or retard- 

 ing effect upon the growth of the other, so that, for ex- 

 ample, a nearh^ circular colony of the fly speck fungus 

 may be almost completely surrounded by sooty blotch, 

 yet the line of demarkation between the two be sharp and 

 clearly marked (Fig. 18). 



In other instances, a colony of one of the two fungi 

 may grow toward a colony of the other fungus, until the 

 two meet, then one may proceed to surround the other 

 but not to grow into it. The condition exhibited is much 

 like that frequently found on agar plates, where colon- 

 ies of fungi or bacteria inhibit the growth of each other, 

 and constitutes a strong argument that fungi which can 

 so inhibit growth of each other are not of the same spe- 

 cies. While this inhibition or antagonism of sooty blotch 

 by fly speck or vice versa is a very common phenomenon, 

 cases do frequently occur where one of these fungi grows 

 into the colony of the other, such as Rhizopus may grow 

 through a colony of PeniciUium. 



The morphology of the cell aggregations of sooty blotch 

 and fly speck is dissimilar as to the size and external ap- 

 pearance (Fig. 18), and internal appearance (Figs. 15, 

 17). 



The mycelium radiating from the cell aggregations of 

 sooty blotch (Fig. 9), has been discussed. The mycelium 

 radiating from the fly speck is very fine and hyaline, and 

 is of quite different character than that of sooty blotch. 



