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



Plate VI. 



Frost Injury to Tsuga mertensiana, Chamaecyparis lawsoniana, and 

 Sequoia washingtoniana. 



A .—Transverse section through frost ring in Tsuna mertensiana, showing the outer face of a pre- 

 ceding growth ring at bolt oin and a large number of well-ligniflei 1 traeheids developed before the 

 sing; also a radial cleft Cat upper left-hand corner) Tilled up with large-celled parenchyma. 

 (X135.) B.— Transverse section through a frost ring occupying a median position in a growth 

 ring of Chamaecyparis lawsoniana, showing an unusually broad zone of dark-brown parenchyma 

 and radial clefts also filled up with large-celled parenchyma. ( X 135.) C— Frost ring occurring 

 at the outer limit of a summer-wood formation in Sequoia washingtoniana, showing a series of 

 radial clefts subsequently filled up with large-celled parenchyma. (X135.) 



