368 



FUNGOUS DISEASES OF PLANTS 



The mycelia of both the blotch and the speck are superficial, at 

 most merely roughening the surface of the cuticle. The blotches 



are irregular in 

 outline, sometimes 

 coalescing into 

 large areas. The 

 specks, as the name 

 indicates, are small, 

 circular, dark col- 

 ored flecks associ- 

 ated in groups, and 

 sometimes distrib- 

 uted over large 

 areas. 



A network of ra- 

 diating olive-brown 

 or fuliginous hyphae 

 made up of more or 

 less barrel-shaped 

 cells constitute the 

 blotch. Cell fusions and cell aggregations are common. On the 

 other hand, the specks are 

 at first dense aggregates 

 of rather light colored hy- 

 phae, and from such specks 

 delicate hyphae may be 

 traced to similar neighbor- 

 ing spots or to blotches. 

 A mature speck becomes 

 shining black and dry. 

 Then the central portion 

 breaks away and is pre- 

 sumably the source of new 

 infections. No spore form 

 has been found accom- 

 panying this phase. Both 



r i FIG. 188. LEPTOTHYRIUM POM/: DEVELOP- 



types of fungus have, MENT QF PYCNIDIA FROM PYCNO SCLEROTIA 



however, been followed (Photograph by B. F. Floyd) 



FIG. 187. FLY SPECK AND SOOTY BLOTCH OF APPLE 



