106 PLANT BIOLOGY 



stock are bound together by grafting wax (Fig. 47, B,c}, which is put 

 around the outer bark to hold the two pieces in place and to pre- 

 vent evaporation. In this way the cambium layers of the two 

 plants are brought into close contact and soon unite. The ducts of 

 the stock likewise join those of the scion, and so sap is transmitted 

 to the grafted twig, which grows and develops its fruit as though it 

 were still a part of the plant from which it was taken. There are 

 many different ways of cutting and binding the twigs together, 

 and even buds may be used as scions (Fig. 47, C, b). But the prin- 

 ciple is the same in every case. 



Grafting is of necessity employed in producing new plants of 

 seedless grapes or oranges. It is also frequently adopted to com- 

 bine the desirable characteristics of two different plants. For 

 example, when the vineyards of France were being destroyed by 

 an insect that attacked the roots, the fruit-growers overcame the 

 difficulty by grafting the wine-producing scions upon the more vigor- 

 ous and resistant nutritive stock of grapevines introduced from 

 America. 



114. Slips, runners, and layers. Another method of producing 

 new plants is that of cutting twigs of plants that are desired, and 



FIG. 48. Strawberry plant with runner. (Bailey.) 



placing the lower end of the stems in moist sand. Roots soon 

 develop on these so-called slips, and the new plants thus formed can 

 then be transplanted into good rich soil. Any one who has seen a 

 vigorous strawberry plant knows that it sends out a lot of slender 

 stems which grow so rapidly that they are known as runners. When 

 a portion of one of these runners lies upon the surface of moist soil, 



