228 
PRUNING AND THINNING. 
[Part IV. 
equivalent to what are called “ the spurs/’ or 
the “ swell of the roots” where they join the 
stem. De Candolle’s observations would apply 
to roots as well as branches. But if we bisect 
them lengthwise, we may see with a glance that 
roots as well as branches stand on increasing, 
not decreasing bases, where they join the stem. 
A dead branch, or an undersized branch, over¬ 
grown by the head of the tree, will cause a 
hollow below it, from stopping the downward 
current from the head, which cannot turn suffi¬ 
ciently short to deposit immediately below the 
branch. This is often seen in beech-trees; and 
the groove is sometimes prolonged the whole 
extent of the stem. 
Indeed, the unity of growth which must exist 
at the foot of each branch, with the part of the 
stem which is above it as well as below it, is 
apparent from the fact that, when branches are 
cut otf at the distance of an inch or two from 
the stem, the descending sap of the bark of the 
stem will ascend the bark of these stumps, will 
well over between their dead upper bark and 
wood, annually increase their girthing, and cica¬ 
trise or heal over their ends, forming protube¬ 
rances which will occasion a consequent distor¬ 
tion of the grain of the wood, and diversion of 
