112 STUDY OP COMMON PLANTS. 



bright color if not too old, and their pulverulent appear- 

 ance. Some of the rust easily adheres to the hand or 

 clothing as an orange-red powder. 



III. Place some of the rust thus obtained under the 

 compound microscope. It will be seen to be made up 

 of spores. Examine their structure carefully, and draw. 

 These are uredospores, or summer spores. 



IV. Examine in the same way the dark spots obtained 

 as directed (I, 2). Notice how they differ externally from 

 the preceding. Prepare specimens as before, and examine 

 with the microscope. Draw some of the dark-colored 

 teleutospores, winter spores. How do they differ from the 

 uredospores in size, form, surface, and other particulars ? 



V. Cut cross-sections of sori containing uredospores, and 

 others of sori with teleutospores, and examine microscopi- 

 cally. The sections must be thin, and should be cleared 

 with potash solution or laid in glycerine. Observe 



1. The mycelium, or vegetative part, of the fungus and 



its relation to the infested leaf. It consists of 

 numerous interwoven hyphse, and accumulates in 

 masses especially in the lacunae of the leaf, though 

 it is not wanting in the tissue beyond them. 

 When spores are formed, the epidermis yields to 

 the increasing pressure from within, and is finally 

 ruptured. 



2. Observe the connection of the spores with the my- 



celium. Notice, too, particularly whether any 

 teleutospores occur in the sori containing uredo- 

 spores, and vice versa. Determine, if possible, 

 whether the same mycelium produces both kinds 

 of spores. If several different ages are compared 



