Some Important Pear Diseases. 



28: 



6. Microscopic Characters. 



A thin section through a diseased spot* is shown in figure 163. 

 Here we see at e the outer cell layer, or epidermis, of the leaf on both 



Y^- 



t 



V.- 



163. — Cross section through a leaf-spot, showing the fruit body and spores of 



the leaf-spot fungus. 



sides. At / is shown the palisade layer of cells often containing so 

 much of the green coloring matter of the leaves, and below this the 



* Portions of leaves showing the fungus, after being properly fixed and 

 dehydrated, were imbedded in paraf^ine, sectioned, and stained. The 

 Ehrlich-Biondi-Heidenhain combination works well, staining green the 

 deadened host cells and older h3'phal elements, while the basidia, younger 

 hyphae, and fresher leaf tissues are colored red. A carmine and nigrosin 

 combination also works well. 



The spores do not germinate very readily in agar alone, but I have 

 secured abundant germination in agar containing pear-leaf decoc- 

 tion. Isolated spores were then removed to bean-steni and pear-steni 



