418 



1 



Illinois Natural History Survey Bulletin Vol. 23. Art. 4 



Siberian — were cultured in the laboratory, 

 1939-1943. Several types of bacteria were 

 isolated from 239, or approximately 69 

 per cent, of the trees sampled. Of the 346 

 trees, 292 had wilted during one or more 

 growing seasons. Many of the remaining 

 54 trees, which were affected with wet- 

 wood but which had not wilted, showed 

 flux. As preliminary tests showed that the 

 various bacterial isolates would grow 

 abundantly in nutrient broth and on 

 potato dextrose agar, these two media 

 were used throughout this investigation, 

 except where otherwise stated. 



Pig_ 17. — A wetwood-affected elm with a 

 trunk crack which had callused over. Callus 

 was formed by both the wood and bark. 



1943 spring wood through which it passed. 

 However, the streaks in the branches did 

 not extend to the branch tips. Other 

 cracks, which were confined within the 

 heartwood, are shown radiating out from 

 the center of the trunk in fig. 9. The sap 

 in this tree was under a pressure of 13.5 

 pounds before the tree was cut. Wetwood- 

 affected tissue extended only to the 

 junction of roots and trunk, fig. 11. 



Isolations 



Samples from 346 elms — American, 

 Moline, Littleford, slippery, English and 



Fig. 18. — The trunk crack shown in fig. 17 

 with the current-season wood removed. Gray- 

 ish brown discoloration formed in the wood 

 along the crack. 



