IMPROVEMENT OF LIVING THINGS 



237 



mately the cost of production, and systematically 



weed out his herd." 1 



Scientific poultry raising results in marked suc- 

 cess. A record is kept of 

 the eggs laid by each hen. 

 This is done by trap-nest- 

 ing. The nests are of such 

 a design that only one hen 

 can enter a nest at a time 

 and she cannot leave until 

 released. Each hen has a 

 numbered tag on her leg 

 and every egg she lays is 

 credited to her. By breed- 

 ing only from the best lay- 

 ers we can increase the av- 

 erage number of eggs laid 

 by a flock. 



Have plants been im- 

 proved by man? All of our 

 domesticated plants are de- 

 scendants of wild ancestors. 

 By taking advantage of 



FIG. 377. EDISON S GOLDEN ROD . . 



This giant plant was devel- variatlons an <l selecting 



oped by crossing and selec- and cross-breeding differ- 

 tion from a common variety, ent types of plants, we have 



kept desirable traits. Some- 

 times plants quite different from their parents sud- 

 denly appear in nature. Our seedless oranges origi- 

 nated in this way. Some one discovered two orange 

 trees growing in South America that bore seedless 

 oranges. These plants were later removed to Cali- 

 fornia, where the buds were grafted on trees that 

 produced oranges with seeds. 



What was the work of Luther Burbank? As a crea- 

 tor of new forms of plant life in this country, Luther 

 Burbank (1849-1926) won for himself much recogni- 

 tion as a benefactor of man. Most of his new and im- 

 proved plant forms were developed on his experi- 

 mental farm at Santa Rosa, California. He used the 

 methods of selection and crossing to obtain his wonder- 

 ful new plants. He was a genius at selecting plants 

 of near relationship showing the traits he wished to 

 establish and perpetuate. He would cover the flower 

 of a certain plant and remove the stamens before pol- 

 len developed. At the proper time he would put on 

 the stigma of this flower some pollen from another 

 plant possessing traits he wished to establish in the 

 first plant. In this way he produced many new varie- 

 ties. These methods of plant breeding are now used 

 in experimental breeding stations operated by agri- 

 cultural colleges, state departments of agriculture, 

 and the United States Department of Agriculture. 

 Burbank produced a great many new flowers, fruits, 



'Bulletin No. 55, U. S. Department of Agriculture. 



KIC. 378. WHITE BLACKBERRIES 



and vegetables. He crossed a cream-colored berry 

 with a blackberry and by selecting for several genera- 

 tions succeeded in ob- 

 taining a large white 

 blackberry (Fig. 378). 

 He crossed the apricot 

 with the plum and de- 

 veloped a new fruit 

 called the plumcot. By 

 his genius a cactus of 

 Arizona has been rid of 

 its thorns and is now 

 used as a food for cat- 

 tle. He produced wal- 

 nut trees that grew 

 seven feet in one year, 

 whereas ordinary wal- 

 nut trees grow less than 

 an inch a year. These 

 are a few of Burbank's 

 achievements. Consult one of the special references 

 for more details of his life. 



Summary. The purpose of this study is to acquaint 

 you with the factors that influence the lives of all 

 living things. Read carefully the following statements 

 which summarize the main ideas developed in this 

 topic. 



1. Offspring resemble their parents because they 

 have received traits and characteristics from them. 

 This is called heredity. 



2. Offspring are never exactly like their parents. 

 This is called variation. Variation is due to (1) en- 

 vironment and (2) the fact that the offspring receives 

 traits from two parents that are not alike ; hence the 

 offspring cannot be like either parent. 



3. Man improves plants and animals by selection 

 and controlled breeding. 



4. Heredity operates by law, and both good and bad 

 traits are inherited. 



5. Heredity, environment, and training are the im- 

 portant factors in the life and progress of man. 



6. It is possible to improve man by weeding out un- 

 fit people, by improving the environment, and by 

 creating better facilities for education. 



REFERENCES FOR FURTHER STUDY 



Texts 



Caldwell and Curtis, Science for Today, Chap. 32 

 Hunter and Whitman, Science in Our World of Progress 



Unit 14 

 Powers, Neuner, and Bruner, The World around Us, Units 



2 and 8; Man's Control of His Environment, Chaps. 1-3 

 Watkins and Bedell, General Science for Today, Chap. 31 

 Webb and Beatichamp, Science by Observation and Experi- 



ment, Unit 9 

 Wood and Carpenter, Our Environment: How We Use and 



Control It, Unit 8 



