PT. iv; 



PRUIS^ING AND THINNING. 



209 



and from DD to EE would have been solid clean timber 

 instead of a disunited knot. So that there would have 

 been no disunited knot at all, but only a cross-grain, 

 formed by the living branch firmly united to the stem, 

 and decreasing^ in size towards the centre of the tree, 

 with a scar at the end D D, like that at E E. This 

 scar would form no greater flaw in the timber, than 

 one arising from a small piece of bark being knocked 

 off the stem. If the branch had not died, the cross- 

 grain would not only have been annually prolonged as 

 long as the tree continued to grow, but woidd also have 

 increased in bulk every year ; for De Candolle's cone, 

 whose apex is at the pith, and whose base at the bark 

 of the stem, describes most accurately the form of the 

 cross-grain occasioned by a living branch in the timber 

 of a tree. If the branch when it died had not been 

 cut off at E E, the existing disunited knot would have 

 been prolonged ; that is, from E E in the direction of 

 F, as long as the tree grew, and the branch remained 

 on it, a disunited knot would have been inclosed in ex- 

 change for the deposit of solid, clean, straight-grained 

 timber. For that the grain becomes straight as soon as 

 the scar is healed over, may be seen in Plate II. 



The sixteenth annual growth above the branch is 

 the last whose descent was checked by the dead 

 branch. Its distance from the centre of the pith of 

 the stem, measured at the upper edge of the board, is 

 four inches one-sixteenth. The distance of the six- 

 teenth annual growth from the centre of the pith 



P 



