614 IMPROVEMENT OF LIVING THINGS BY MAN 



to another tree of a nearly related kind (called the stock). The 

 two parts must be so placed that the cambium surface of the scion 

 comes in contact with the cambium of the tree to which it is ap- 

 plied, thus putting it in direct communication with a supply of 

 food from the tree which is already established. Peach, apricot, 

 apple, and pear trees are often grafted. Another similar method is 

 called budding. A bud of the desired tree is inserted under the 

 bark of the stock. The branches growing from the bud or scion 

 will bear the same variety of fruit as if they had remained on 

 the original tree. Grafting and budding are widely used by plant 



breeders to per- 

 petuate desirable 

 kinds of plants. 



Grafting is also 

 practiced in ani- 

 mals. Hydra, 

 worms, insects, and 

 frogs all have been 

 used experimen- 

 tally. Surgeons 

 graft skin after a severe burn, or graft glands in sheep, goats, or 

 other animals and sometimes, but very rarely, in man. In all of 

 these cases the same thing takes place as when we cut ourselves and 

 the wound heals : new tissues are formed by the growth of cells. 



Home Project. 



it to the class. 



pro- 



Professor Morgan grafted parts of earthworms and 

 duced (1) a very long worm, (2) a two-tailed worm, (3) a very 

 short worm. 



Make a successful bud or graft and demonstrate 



Practical Exercise 4. Make a table in which you have as headings all the 

 different ways in which plants or animals are "propagated." Under each 

 heading place examples that you have personally seen. 



Practical Exercise 5. Find out from such a magazine as Hygeia all the 

 reliable information you can about gland grafting. Compare this with adver- 

 tisements on gland grafting taken from newspapers. Do you believe the 

 advertisements ? Why ? 



Practical Exercise 6. List ten useful fruit trees that can be grafted. Con- 

 sult a fruit grower. 



Vegetative propagation and reproduction. When, as in the 

 above examples, a new plant is produced from a portion of a plant, 

 generally used for nutrition, the process is called vegetative propaga- 

 tion or growth. Vegetative propagation is a form of asexual repro- 



