MOTJLDS, E0STS, ETC. 113 



by using material gathered at different times, it 

 will not be difficult to make out the relation of 

 the two forms of spores to each other. 



3. Examine more in detail the structure of the mycelium. 

 Choose an isolated portion, and draw. Trace it 

 into the intercellular passages of the leaf, and 

 follow it as far as it extends. 

 What is the effect of the presence of the fungus on 

 its host (the plant infested by it) ? 



VI. Prepare sections of the barberry leaf so that they 

 will include true longitudinal sections of the secidium fruit, 

 and examine microscopically. 



1. With the low power, study the general features, and 



make a sketch showing the cup-like structure with 

 its base immersed in the leaf, the walls composed 

 of thickened cells, and the rows of spores. 



2. With the high power, study each part in detail. 



a. The mycelium, thickly massed at the base of the 

 cup and extending widely through the swollen 

 portion of the leaf. How does it compare with 

 that seen in the wheat leaf ? 



h. The wall of the secidium fruit. Notice the pecul- 

 iar modifications of the elements composing it. 

 Is it properly a part of the fungus or of the 

 host? Study carefully the thinnest sections at 

 the base of the cup, where the mycelium is most 

 abundant, if you are at a loss to determine. 



e. The form, structure, and arrangement of the spores. 

 Observe how they originate, and notice the effect 

 of mutual pressure. 



