THE LILAC MILDEW. 



Microsph&ra alni or M. quercina. 



THALLOPHYTES; FUNGI; ASCOMYCETES. 



PRELIMINARY. 



THE lilac mildew, Microsphara alni, is extremely com- 

 mon in the United States, making the upper surface 

 of the leaves look white and moldy from midsummer on. 

 M. quercina is quite common upon oak-leaves and is 

 equally favorable for study. The first stage at which 

 the Fungus is ready to gather is when it appears powdery, 

 which is usually in June or July, the earlier collections 

 being the best. The next gathering should be made 

 in the early part of September, and another just before 

 the leaves fall. As the leaves bearing the Fungus are 

 gathered, lay them in a book or plant-press to dry. If 

 it is possible to examine the first stage with fresh material, 

 it will prove more satisfactory, but for the remainder 

 dried material will answer quite as well. Specimens 

 of the first and second collections preserved in alcohol 

 or formalin will often prove helpful in the work. 

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