PROPAGATION (:>! 



acteristics as in most of our tree fruits, plants produced by- 

 sexual methods yield a very inferior quality of fruit. 



Asexual methods of propagation all differ from sexual, 

 since the offspring is grown from a group of cells from one 

 plant and, therefore, has always exactly the same protoplasm 

 or germ plasm as that of the parent. This is possible because 

 a small portion of a plant can regenerate a complete plant. 

 A bud always arises by the division of cells as described in 

 Chapter 4, and therefore has exactly the same gene combi- 

 nation. Thus any number of cuttings or grafts made from 

 the same plant will produce plants that are the same in all 

 their general characteristics. For this reason fruits, roses, 

 and many trees are usually propagated by some asexual 

 method. Such a group of plants produced asexually from a 

 plant is known as a clone. 



It is clear from the above that for plant breeding the 

 sexual methods of propagation will give a wide variety of 

 plants. This is covered more fully in Chapters 18 and 19. 

 If uniformity is desired some asexual method of propagation, 

 such as cutting, grafting, budding, or layering, must be 

 utilized. 



A cutting is a small piece cut from a stem, root, or leaf, 

 which will produce a complete plant like the one from which 

 it came. Cuttings must form a root-promoting hormone, 

 before roots are initiated, which may require only a week or, 

 for some plants, it may take as long as several months. Dur- 

 ing the last two or three years a number of chemicals have 

 been found which appear to stimulate the hormone forma- 

 tion or perhaps to act like the hormone (Plate X). This is 

 discussed more fully in Chapter 20. 



Stem cuttings are of two kinds, dormant wood and green 

 or growing wood cuttings. They must be from healthy tis- 

 sue, usually four or five inches long, with one or more buds 

 and a good supply of stored food. Dormant cuttings are 

 made in the fall and stored in a cool moist place until early 



