PROPAGATION BY MEANS OF CUTTINGS 95 



Wounds on plants begin to heal by the formation of loose 

 cellular matter which gives rise to a mass of tissue known as a 

 callus. This tissue eventually covers the entire wound, if 

 complete healing results. Usually, the first apparent change 

 in a cutting is the formation of a callus on the lower 

 end, and it is commonly supposed that this process 

 must be well progressed before roots can form. Yet 

 roots do not arise from the callus itself, but from 

 the internal tissue, and in many plants they appear 

 to bear no relation in position to the callus. In 

 willows, for example, roots arise from the bark at 

 some distance from the callus. Yet, as a matter of 

 practice, best results are obtained from callused 

 cuttings, particularly if the cuttings are made from 

 mature wood, but this is probably due to the fact 

 that considerable time is required for the formation 

 of the adventitious buds which give rise to the 

 roots, not to any real connection between the cal- 

 lusing and rooting processes. 



Hardwood dormant cuttings give better results 

 when kept inactive for some time after they are 

 cut. They are usually made in autumn, and stored 

 over winter in sand, sawdust or moss in a cool 

 cellar, or buried in a sandy and well-drained place. 

 This, at least, is the practice with hardwood cut- 

 tings of deciduous plants, as currants, gooseberries, ^ IG 100 

 grapes and many ornamental trees and shrubs. Mallet cut- 

 Hardwood evergreen cuttings, when taken in au- ^|) * 

 tumn, are usually set at once, as their foliage will 

 not allow them to be buried with safety; but in this case, 

 the cuttings are kept "quiet" or dormant for a time, to 

 allow callusing to progress, as in a pit (Fig. 97). If cuttings 

 are buried so deep that they cannot sprout, callusing may be 

 hastened by placing them in a mild temperature. Single-eye 



