FUNGI AND FUNGOUS DISEASES OF PLANTS 245 



Q- 



growths of the mildew. Another complex method of reproduc- 

 tion results in forming a heavy-walled body, the ascocarp, so 

 called because it is the body which contains the sacs and asco- 

 spor'es (fig. 190). In late summer the ascocarps may, without 

 magnification, be seen as small black bodies upon the surface 

 of lilac leaves. When the ascocarp is broken, the sacs and 

 spores are exposed. From the walls of the ascocarp peculiar 

 arms extend, and in the lilac mildew and some related mildews 

 these have strikingly branched tips. 



The heavy -walled asrorarp is resistant 

 to unfavorable climatic conditions. It 

 may pass through the winter and break 

 open In the following spring, thus free- 

 ing the thin-walled sacs. Upon escaping 

 from the sacs the spores may be blown 

 or carried about and germinate upon 

 new host leaves. 



233. Blue mold or green mold. When 

 old shoes, gloves, or other articles made 

 of leather are left in damp, warm places, 

 a blue or green mold (^Penicillium) fre- 

 quently develops upon them. This mold 

 also grows upon old lemons and oranges, 

 and upon cheese. Various species have 

 distinctive shades of color, so that the 

 common names of blue mold or green 

 mold can be taken only as applying in a general way. Certain 

 species of Penicillium are said to give characteristic flavors to 

 the cheese in which they grow, as Penicillium Roqueforti of 

 Roquefort cheese and Penicillium Camemberti of Camembert 

 cheese. These species are widely distributed and are found 

 growing upon many substances besides cheese. 1 Penicillium 



1 An interesting discussion of various species and their cultural reactions 

 is "Cultural Studies of Species of Penicillium^' 1 by Charles Thorn, Ph.D., 

 Mycologist in Cheese Investigations, Bulletin 148, Bureau of Animal Indus- 

 try, U.S. Dept. Agr., 1910. 



FIG. 191. The blue mold 



At the left is the tip of a 

 hypha, with the character- 

 istic branches, on the ends 

 of which are the spores ; at 

 the right are germinating 

 spores. Much magnified. 

 After Thorn 



