246 Principles of Plant Culture. 
C— ProtEcTIVE PRUNING 
429. Dead or Dying Members of a plant Should Be 
Promptly Removed, since they more or less endanger its 
well-being. Dead branches of any considerable size invite 
decay into the stem which often results disastrously (418). 
Branches that are dying from infection by a fungous para- 
site, as with the apple or pear blight, or the black knot of 
the plum (323), are especially dangerous and should always 
be removed as soon as discovered. Branches that tend to 
interfere with the growth of others already formed should 
be checked by pinching, and those that interfere by too 
close contact should be cut back in proportion to the inter- 
ference. 
D—MartvraTIveE PRUNING 
430. This is seldom practiced. In nursery trees that 
tend to grow too late, and thus to endanger winter killing, 
the leaves are sometimes removed two or three weeks before 
the time when hard frosts are expected, to encourage ripen- 
ing of the wood. 
The later tobacco plants in a plantation are usually top- 
ped at the time the main crop is pushing the flower stalk, 
which causes their leaves to mature in season to be harvested 
with the rest of the crop. 
431. The Principal Pruning Implements are the fol- 
lowing: 
The pruning knife (Fig. 164) is useful for removing small, 
woody shoots. The blade should be of good steel, and the 
point should curve forward a little, to prevent the edge from 
slipping off the branch. The handle should be large to 
avoid blistering the hand; the base of the blade should be 
thick to furnish a support for the thumb, and the rivet 
