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Illinois Natural History Survey Bulletin 



Vol. 23, Art. 4 



Fig. 9. — Cross section of trunk showing a crack that extends from wetwood-atfected heart- 

 wood through the bark. Also visible are cracks radiating from the center of the heartwood. 

 Cracks in the wood aid in spread of sap and gas in wetwood-affected trees. 



branch has been removed, fig. 4, and 

 around trunk cracks through which it 

 flows, fig. 8. Young shoots directly above 

 fluxing regions may wilt. Foliage and 

 young shoots, and also the grass at the 

 base of an affected tree, may be killed if 

 the flux drips on them. 



At Hinsdale, in June and July of 1943, 

 several affected elms having splits or 

 cracks in the trunk bark were examined. 

 Fluxing made the bark cracks on these 

 trees conspicuous, fig. 6. When the cracked 

 bark was removed, corresponding cracks 

 were found in the wood beneath, out of 

 which sap had been oozing, fig. 8. Cross 

 cuts of these trunks showed the cracks in 

 the wood to extend inward into wetwood- 

 affected tissues, fig. 9. Cracks in the heart- 

 wood radiated from the center and extend- 

 ed through several woodrings, fig. 9. Most 



of these cracks did not reach the cambial i 

 region; therefore, they did not flux, al-! 

 though they may possibly have permitted 

 more rapid and greater internal move- 

 ment of sap and gas. 



Cracks probably develop in the wood 

 during the winter months, at times when 

 the temperature falls rapidly to very low 

 points. Toxic sap from the wetwood- 

 affected heartwood kills the cambium for 

 some distance around the cracks in the 

 wood. The bark separates from the wood 

 forming oval to elongate pockets, fig. 8. 

 Cracks in the bark with flux oozing 

 through them become apparent in June 

 or July. Many such cracks callus over 

 during the same growing season, fig. 10. 

 In studying Platanus acerifolia Willd. 

 which had developed frost cracks, Crandall 

 (1943) found only wetwood-affected tree; 



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