216 PRINCIPLES OF PLANT CULTURE 



(21) sometimes unite by grafting ; examples, the chest- 

 nut unites with the oak ; the pear unites with the thorn. 



Plants belonging to different families rarely unite 

 by grafting. The oak and walnut and the fir and linden 

 have been grafted. 



The apparent resemblance of two plants of different 

 species is not always evidence that they will unite by 

 grafting, e.g., the peach and apricot, though resembling 

 each other in many respects, do not readily unite by 

 grafting, but both unite freely when worked upon the 

 plum, though the latter apparently differs from both 

 the peach and apricot more than these differ from each 

 other. 



Many plants unite freely when grafted in one direc- 

 tion, that fail to unite when worked in the opposite 

 direction; e.g., many cultivated cherries united freely 

 when worked upon the mahaleb cherry, while the latter 

 fails to unite when worked upon any of the cultivated 

 cherries ; many pears unite freely when grafted upon 

 the quince, but the quince does not freely unite when 

 worked upon the pear. The only sure way of deter- 

 mining what species may be united by grafting is by trial. 



These principal kinds of grafting are in use, viz., cion- 

 grafting, budding and approach grafting. 



386. Cion-grafting is used in grafting on roots (root- 

 grafting) and very often in grafting on the stem, especially 

 on large trees. The cion is a portion of the dormant 

 stem, of the variety it is desired to propagate. It should 

 generally be of the preceding season's growth and should 

 always contain one or more healthy leaf-buds (131). 

 Flower-buds are occasionally used, but should be avoided 

 except in special cases. It is probably best to cut cions 

 from trees known to be fruitful. Cions are usually cut 



