CHAPTER VIII 



THE USE OF SHOOTS FOR PROPAGATING 



§ 34. What is meant by layering, and of what use is it ? 



A NUMBEK of shrubs have the faculty of readily producing 

 adventitious buds. Such buds are not formed like the regular 

 eyes in the young tissues at the tip of the stem, but take 

 their origin at a later period, and usually in consequence of 

 some external stimulus. The pith of these buds is not con- 

 tinuous with that of the shoot on which they are borne, but 

 joins on to those layers which were the formative tissue or 

 cambium in the year in which these buds took their origin. 



Dormant buds, too, may grow out many years after the main 

 shoot is formed, but they were formed in the same year as 

 the shoot itself, and their pith is continuous with that of the 

 shoot. 



Such adventitious buds may arise on roots and grow out 

 into shoots, and if separated with a portion of the root of the 

 parent plant, become separate individuals (Raspberry, Lilac, 

 some kinds of Plums, Cherry, Apple, Spirea, Rose, &c.). 



On the other hand, many plants can produce adventitious 

 roots from leaf and stem structures if they receive a certain 

 stimulus. Gardeners use this faculty for purposes of propa- 

 gation by stimulating branches or shoots to produce adven- 

 titious roots, and then separating them from the parent plant. 



Sometimes by merely increasing the supply of sap a branch 

 may be stimulated to produce adventitious roots. In other cases 

 more potent irritation (such as is produced by a wound) must 

 be set up to produce the desired effect, and it takes a longer 

 time until the result is attained. In such plants, in which 

 the formation of roots is difficult to bring about, the gardener 

 endeavours not to damage the shoots which are to be experi- 



