Bui. 1131, U. S. Dept. of Agriculture. 



Plate II. 



Frost Injury to Thuja plicata, Pseudotsuga taxifolia, and Larix 



occidentalis. 



A . — Transverse section through frost ring in Thuja plicata, showing a pronounced distortion of 

 the medullary rays. (X 135.) B. — Transverse section through frost ring in Pseudotsuga taxifolia, 

 showing the crumpling of the wood cells that were but slightly lignified at the time of freezing. 

 (X135.) C. — Transverse section through frost ring in Larix occidental is sapling (tree No. 1), at 

 146 centimeters above the ground, showing an extreme case of lateral displacement of the 

 medullary rays. (X135.) 



