100 LABORATORY AND FIELD EXERCISES 



RUSTS 



1. Examine leaves of cereals or other plants on which the 



different kinds of spores of a rust are borne. Can you 

 see differences in color or form of the different kinds 

 of rust spores ? Are the spores borne in groups or 

 masses ? -Where is the mycelium from which these 

 spores originated ? How do the spores become exposed 

 to the air ? On how many and what kinds of hosts are 

 the different kinds of spores borne ? 



2. Draw the stem or leaf surfaces on which spores are borne 



showing the groups of spores, or sori, of each kind pro- 

 duced by the species being studied. Name the host and 

 the kind of spore in each drawing. 



3. Examine the different kinds of spores of the rust micro- 



scopically. How do they differ ? How are they adapted 

 for distribution and wintering ? 



4. Draw each type of spore in some detail. 



5. Life history. How many hosts are infested by the rust 



you are examining ? What are the spring, summer, and 

 winter spores ? What is the function of each in the life 

 history ? 



SMUTS 



1. Examine corn or other cereals infested with smut. Tease 

 out some of the dark mass on a slide and examine micro- 

 scopically. What is the composition of these dark smut 

 masses ? Draw some smut spores. Where is the plant 

 which gave rise to the spores ? Is it a parasite ? How 

 do the spores become exposed to the air ? When and 

 how do these spores infect a new crop ? 



