CIRCULAR NO. 61. 



United States Department of Agriculture, 



BUREAU OF ENTOMOLOGY, 

 L. O. HOWARD. Entomoloeist. 



BLACK CHECK IN WESTERN HEMLOCK. 



By H. E. BUEKE, Special Field Agent. 



ECONOMIC IMPORTANCE. 



Black check is the lumberman's name for a common defect, consist- 

 ing of a dark brown or blackish resinous scar, in the wood of the western 

 hemlock. A few layers of the wood beneath this scar are slightly 

 stained for a short distance around, and all 

 of those above are thickened, curled, or in 

 some way abnormal. When seen in a 

 quarter-sawn board (radial section) the 

 defect appears as a small, thin seam (fig. 1) 

 from one-half to one inch long, with one 

 side curly. In a bastard-sawn board (tan- 

 gential section) it is an oval or circular 

 spot (fig. 5, g) that varies in diameter from 

 one-half to one inch. In both cases it lies 

 with the grain of the wood. 



Hemlock timber growing on lowlands 

 is often seriously affected, while that on 

 higher land, especially above an altitude 

 of 1,800 feet, appear* to be free from the 

 injury. In a large quantity of box stock 

 cut from lowland timber, nearly every 

 board examined hj the writer contained 

 numerous examples of the defect. 



Timber badly affected with this defect 

 is nearly worthless for finishing, turning, 

 staves, and woodenware, for which it would 

 otherwise be excellent. The injury is very 

 conspicuous in bastard-sawn lumber, un- 

 fitting it for finishing or turning, while in that quarter-sawn (fig. 1) or 

 cut across the grain it is apt to form an open seam which renders it 

 worthless for staves and woodenware, where tightness is required, but 

 it would appear that it is not materially detrimental to timber for con- 

 struction and other purposes. 



Taking into consideration the common occurrence and injurious effect 

 of the blemish in lumber for certain purposes, and the large amount of 

 timber concerned, the total loss caused by the check must be considerable. 



Pig. 1.— Longitudinal Eection of 

 a board approximately quar- 

 ter-sawn containing cheeks 

 (radial section) (original). 



