

ULmus 



. 



. Litmus . 



Plate %. 



PLATE II. 



Fig. 5. Cross sections of an Ulmus (American elm) growing in region 6 of 

 the Aliquippa district near the mill and showing the distinct effect of smoke 

 and gases. 



Fig. 6. Cross sections of an Ulmus (American elm) growing on the hillside 

 !n region 5, Aliquippa district. Shows a tendency toward a narrowing of rings. 

 Evidently effected by the smoke and gases from the trains. 



