70 THE LILAC MILDEW. 



LABORATORY WORK. 



GROSS STRUCTURE. 



I. GENERAL CHARACTERS. Observe. 



1. The"distribution of the Fungus on the surface of the leaf. 



2. The color. 



II. THE CONIDIOSPORES. Observe: 



i. The pulverulent appearance on the leaves first gathered, 

 caused by the abundant conidiospores. 



III. THE FRUIT. Observe: 



1. The black dots on the leaves gathered later in the season, 

 the spore-fruits, or ascocarps. 



2. Associated with the black dots, other yellow ones, the 

 immature ascocarps. 



MINUTE STRUCTURE. 



I. THE MYCELIUM. 



Scrape the Fungus from the surface of a leaf gathered in 

 early summer. First moisten it with dilute potassic hydrate 

 if the specimen is a dried one, and under high power observe: 



1. The colorless filaments of the mycelium. 



a. The branching. 



b. The irregular diameter. 



c. The rarity of partition-walls. 



2. Small lateral expansions of the filaments, haustoria, some- 

 what like irregularly indented disks with very short thick 

 stalks, generally difficult to find. 



3. Draw. 



II. CONIDIOSPORES. 



Prepare a slide as before from a pulverulent surface, and 

 observe: 



