264 DISEASES OF TREES 



are often induced to throw out strong shoots, and to show 

 vigorous and persistent growth, by setting fire to the whole 

 wood. 



INJURIES TO THE ROOTS 



These are partly due to animals, e.g. mice, but are mostly 

 caused during cultural operations, and are always prejudicial to 

 the plants. The greatest care must therefore be exercised to 

 preserve the roots during lifting, transport, and planting. 



Pruning the roots is always an evil, and is admissible only in 

 two cases. The first occurs when roots are crushed, nipped, or 

 broken off during the process of lifting. A clean cut imme- 

 diately above the damaged part encourages the formation of a 

 callus from which adventitious roots are produced, and also 

 prevents or reduces the chances of decay in the roots. The 

 second case where shortening the roots is admissible occurs 

 where it would be too expensive to preserve the whole root- 

 system during the operations of lifting and planting. It may be 

 mentioned that many plants suffer less from their roots being 

 shortened than from their being doubled back during planting. 

 In order to induce the formation of a dense mass of roots by the 

 production of numerous roots in the neighbourhood of the collar, 

 repeated shortening of the roots may be necessary where the 

 attainment of extra large plants is the object in view. 



The practice, which is unfortunately still so common, of 

 aimlessly cutting back the roots is in the highest degree 

 reprehensible. 



Other forms of root-injury are occasioned by removing litter 

 from woods, tearing up roots, the attack of cockchafer grubs, 

 mice, &c. 



CUTTINGS 



The growth and future success of parts entirely destitute 

 of roots, e.g. slips, pole-cuttings, &c., depends essentially upon 

 the greatest possible restriction of evaporation from the plants 

 until they have produced an abundant supply of roots. For 

 this reason one at first suppresses the development .of leaves 

 by almost entirely burying the cutting, so that only the highest 

 bud is able to produce a shoot ; or, in other cases, and more 



