148 



PLANT TKOPAGATIOX 



orders, 890 genera and 4,200 species listed in Gray's Field, 

 Forest and Garden Botany, 110 orders, 650 genera and 

 3,000 species come under this ruling and (theoretically) 

 may be grafted, while the balance, the endogens which 

 lack the cambium sheath (oat, bamboo, palm) cannot 

 be grafted. With experimental exceptions (Chapter 

 XII) this is so. 



Among exogens botanical relationship seems in most 

 cases to be fundamental to success in graftage which is 

 usually easy between varieties of the same species (apple 



FIG. 132— GREATLY MAGNIFIED SECTION THROUGH YOUNG GRAFT, 

 Round mass of scar tissue near center merely accidental. 



Upon apple) and often between closely related species 

 (pear upon quince, or plum upon peach). Sometimes 

 species more remotely related than the genus will prove 

 successful ; for instance, apple or pear {Fyrus) upon 

 thorn (CratccgHs). But rarely, and then mostly experi- 

 mentally, can distantly related species be grafted suc- 

 cessfully ; probably not at all from a business standpoint. 

 A few instances may emphasize these points. While 

 pear is commercially grafted upon quince to form dwarf 

 trees, apple is seldom or never so treated, and quince 



