BUDDING AND GRAFTING. 123 



tissue, thrown out by such parts as have the power of generating 

 it. This power does not exist in the heart wood nor in the outer 

 bark, but only in the alburnum or rather the substance imbedded 

 between the alburnum and the inner bark, constituting the 

 cambium. 



Mr. Knight says the effects produced upon the growth and pro- 

 duct of a tree by grafting are similar to those which occur when 

 the sap is impeded by a ligature or by the destruction of a circle 

 of bark ; it acts by obstructing the descending sap, and so causes 

 fruitfulness. The modification effected by the graft therefore is a 

 subject of practical interest and importance to the grower or 

 cultivator, for although the graft alters neither the species nor 

 the variety of the stock it has considerable influence on its habits 

 as well as on the production of fruits and flowers. 



Affinity of Species. Graft and Stock. — Plants of the same 

 family have an analogous origin and can be grafted only on one 

 another with a prospect of success. The success of the operation, 

 even within the family limits, will not always be complete; per- 

 haps from some difference in their organic structure. In such 

 cases practical experience must necessarily become our guide. 

 The pear and the apple can be united onl}' for a short period. 

 Soft- wooded plants do not succeed well with hard-wooded ones, 

 nor ligneous plants with herbaceous ones. The peach and the 

 apricot are grafted on each other with difficulty, while both do 

 well on the plum. Most cherries do well on the Mahaleb, but the 

 Mahaleb does not succeed well as a graft on other cherries. 

 The sweet chestnut will graft on the oak, but will not on the 

 horse-chestnut. The medlar, which has solitary flowers, does 

 well on the thorn, whose flowers are in corymbs. The Ckiouan- 

 thus, so nearly allied to the lilac with its panicled flowers and 

 simple leaves, will do well only on the European or flowering ash, 

 which has compound leaves. The Photinia, allied to the beam tree 

 (Pyrus Aria), and the Eriobotrya, allied to the medlar, both 

 evergreens, will graft on the medlar, and not on the hawthorn. 

 The cotoneasters, amelanchiers, and Pyrus Aria all do well on the 

 hawthorn, and by experience last longer, but make slower growth 

 than they do on the mountain ash. Pyrus arbutifolia grafts well 

 as standards on the mountain ash. Berheris aquifolia will grow 

 on the common barberry, and Primus Lauro-Cerasus does well 

 on the Bird cherry. 



