672 WHO ARE SOME OF THE MAKERS OF BIOLOGY? 



blackberry. Then he selected for breeding the best Irybrid berries 

 for several generations, and finally succeeded in obtaining a large 

 white blackberry with a pleasing flavor. By crossing plums which 

 were resistant to cold and frost with plums which had many other 

 desirable qualities, he obtained a large juicy plum with a small 

 stone, and which will grow in practically any conditions of climate 

 and soil. He produced rapid-growing walnuts, and many other 

 new forms of fruits and vegetables. His work was almost entirely 

 hybridizing and he destroyed thousands of plants in order to obtain 

 the ones with exactly the qualities he wished to perpetuate. He 

 estimated that he raised over 1,000,000 plants every year for 

 breeding purposes. At his death there were over 5000 different 

 foiTQS of plants growing on his experimental farm. 



Self-Testixg Exercise 



Boveri discovered that the (1) and (2) before 



fertilization had just (3) the number of chromosomes found 



in the (4) (5). Gregor Mendel worked out certain 



(6) of (7) in (S). These have been 



(9) today by many plant and animal (10). Luther 



Burbank improved plants largely through (11) and 



(12). 



Achievement Test 



1. What are some names of persons, not mentioned in this unit, 

 who are well known in modern biological sciences ? In medicine ? In 

 public health? 



2. How would you classify the names in this unit under the headings 

 given and tell two things for which each person is famous? 



3. Why is Mendel's work on heredity considered so important ? 



Useful References 



Darwin. Life and Letters of Charles Darwin. (D. Appleton & Co. 



1911.) 

 De Kruif. Microbe Hunters. (Harcourt, Brace & Co. 1926.) 

 Downing, Science in the Service of Health. (Longmans, Green, & Co. 



1930.) 



