Fig. 1. Greatly enlarged cross section of rose leaf (a) affected with an external 

 fungus, the powderly mildew. Both the mycelium and spores (b) are entirely 

 external. The fungus sends suckers (c) into the epidermal cells to get nourishment. 

 (Drawing by H. Hasselbring of the Illinois Experiment Station.) 



Fig. 2. Greatly enlarged cross section of carnation leaf affected with an internal 

 fungus, the carnation rust. The mycelium (a) grows wholly within the leaf 

 between the cells (b). Only the spores appear at the surface. 



(Drawing by H. Hasselbring of the Illinois Experiment Station,) 



