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 Tsuga mertensiana, showing the outer face of a pre- 

 ceding growth ring at bottom and a large number of well-lignified tracheids developed before the 

 freezing; also a radial cleft (at upper left-hand corner) filled up with large-celled parenchyma. 

 (X 135.) 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.) 



