56 A TEXT-BOOK OF BOTANY 



bark. In this way old inscriptions have often been un- 

 covered. 



The well-known operation of grafting depends upon 

 the ability of plants to heal wounds. The plant upon 



which the operation is 

 performed is called the 

 S stock, and the twig graft- 



M t ed into it the scion. An 



% I ordinary method, called 



m cleft-grafting, is to cut off 



11 M the stem or a branch of 

 . fl the stock, split the stump, 



insert into the cleft the 

 wedge-shaped end of the 

 scion, and seal up the 

 wound with wax or clay. 

 The cambiums of the 



HI stock and the scion must 



be put into contact at 



some point; and hence it 



A is usual to insert a scion 



FIG. 55. Cleft-grafting showing scions in in each side of the cleft, 

 place (A)" and the wound sealed with gmce fa e cambium of the 

 clay or wax (B). 



stock is comparatively 



near the surface (Fig. 55). The cambium of stock and 

 scion unite, the wound heals, and the scion becomes as 

 closely related to the activities of the stock plant as are 

 the ordinary branches. The scions are usually cut in the 

 fall, after the leaves have fallen, are kept through the winter 

 in moist soil or sand, and the grafting is done in the spring. 

 A number of important things are secured by grafting, but 

 chief among them is the perpetuation of useful varieties 

 with certainty and at a great saving of time. 



(2) Monocotyledons. In this great group of plants tne 

 vascular bundles of the stem are not arranged so as to form 



