THE SAC FUNGI (ASCOMYCETES) 229 



by destroying the infected fruits and twigs. Spores are so gen- 

 erally distributed that spraying is also necessary. Different 

 sprays have been used, but with such varying success that 

 the advice of local experiment stations should be sought for 

 the special needs in each state. 



222. The morel (Morchelld). Another representative of the 

 open-fruiting ascomycetes is that commonly called the "morel 

 mushroom" (Fig. 184). Its mycelium grows in earth that is 



FIG. 185. Leaves of lilac upon which lilac mildew appears in whitish patches. 

 Also the small dark reproductive bodies are shown 



very rich with decaying organic matter. It is usually found in 

 woods among the leaves and about old logs and stumps. The 

 fruiting body, the mushroom, is the only part usually noticed, 

 and under favorable conditions of moisture and temperature it 

 develops in a very short time, growing at the expense of food 

 material that is gathered by the underground saprophytic my- 

 celium. In the deep, wrinkle-bordered pits of the mushroom 

 are the ascus-bearing hyphse. The ascospores form in great 

 numbers and are so light that they may be widely distributed. 

 223. The powdery mildews: lilac mildew (Microsph&ra alni). 

 Good illustrations of the inclosed-fruited ascomycetes are had 

 in the powdery mildews. They are frequently found upon the 

 surfaces of leaves of lilac (Fig. 185), and related mildews are 



