CEPHALOSPORIUM WILT OF ELMS 9 



The Disease 



Small pieces of infected twigs showing pronounced discoloration were prepared 

 for sectioning. The wood was first boiled in water to remove air; part of the 

 wood was then embedded in celloidin according to Wetmore's (26) adaptation 

 of Jeffrey's method and the rest was sectioned directly without embedding. 

 All of the twigs were sectioned with the sliding microtome. For the purposes of 

 the present studies, both methods of preparation were equally satisfactory. 

 Some of the sections were stained with Haidenhain's haematoxylin and safranin. 

 However, unstained sections not only yielded much better results, but also were 

 simpler to prepare. Whether or not embedding of diseased twigs in celloidin and 

 detailed staining of sections might be more valuable in studies extending over a 

 long period of years, could not be predicted from the relatively limited observa- 

 tions reported here. 



Fungus hyphae were found to be present in the vessels and tracheids of the 



Figure 6. Longitudinal Section of Infected Elm Wood, showing fungus hyphae and tyloses 

 I the vessels, (x 800) 



