THE FUNGI. 



159 



other interesting Rust. These 

 cedar apples, if examined in 

 autumn or winter, are seen 

 to be covered with elevations 

 under the bark. They are 

 now in good condition for 

 study. Thin sections show 

 the spores in their sacs. The 

 bark over the elevations breaks 

 away in the spring and the 

 rust-colored spores appear on 

 the surface. These spores are 

 the teleutospores. They will 

 not grow on the Cedar, but 

 if, borne by the wind, they 

 fall on the leaves of the Apple 

 or Hawthorn, they grow and 



a 



FIG. 91. Cedar apples (Gymno- 

 sporangium davipes) . (Farlow.) 



produce another kind of 

 spore the kind that 

 flourishes on Cedar. 



The shape of the te- 

 leutospores determines 

 the classification of the 

 Rusts ; in all other 

 stages the different 

 kinds of Rusts resem- 

 ble one another so 

 much that they can- 

 not be distinguished. 



No sexual reproduc- 

 tion is known, though 

 it is supposed that it 

 does exist. 



FIG. 92. Corn Rust, Piiccinia maidis. a, 

 section of leaf, showing teleutospores; 6, 

 uredospores ; c, teleutospores. (Clinton.) 



References for Reading. 

 Goebel's " Classification 

 of Plants," pp. 126-131; 



