QUESTIONS 33 



No record of its history is known. The individual tree producing 

 the desired fruit was named. From this grafts and buds have been 

 its only means of propagation. The same is true of many other 

 fruits and vegetables. 



FIELD AND LABORATORY EXERCISES 



1. Effects of Environment. Bring to the laboratory weeds or other plants 

 that have been growing in dense clusters, and, to compare with these, the 

 same kinds of plants grown in open spaces. What differences are noticeable? 

 What is the influence of the environment shown here? Why do trees grow tall? 



2. Take two boxes of growing corn, each a few inches high, that have 

 grown under the same conditions of environment. Place one of these in a 

 warm room in a light window. Place the other in a cool room with less light. 

 Note the difference in growth during the next week. Let all conditions of 

 moisture, air and plant food be maintained as before. W'hat influences of 

 environment are here shown? 



3. The value of selection may be studied in a group of tomato plants, 

 some of which are affected with blight. Select plants which seem to be strong 

 and vigorous in spite of the presence of the disease. If tomato plants are not 

 available for this, use alfalfa or any other plants where a disease exists. 



4. Variations among plants should be examined, and a full list of their 

 variations may be made. Why are some taller than others? Why do some 

 have small and others slender stems? Why are some darker in color than 

 others? Why are some more leafy than others? Would it be possible to 

 establish an ideal for the kind of plants you are studying and select those 

 which most nearly approach that ideal? 



5. Each student should determine, if possible, five or more examples of 

 adaptation to surroundings among plants which he may observe in window 

 boxes, gardens, along roads or on farms. 



6. Hybridizmg.^-Students will understand the possibility of hybridizing 

 much better if they practice cross-pollinating among a number of flowers. 

 Let the pollen from red corn be placed on the silks of white corn. Or any 

 other similar plants or crops may be used in the exercise. 



7. Testing Mendel's Law. A good home project would be to take some 

 one line of plants, as white or yellow corn and test so far as possible the work- 

 ing of Mendel's law. This can be carried at least to the second generation. 



QUESTIONS 



1. Define and illustrate what is meant by heredity in plant breeding. 



2. Of what value is variation to one who is trying to improve a certain type 



of plant? 



3. What is the meaning of mutation? Give examples of this. 



4. Define and illustrate reversion. 



5. Illustrate what we mean by the environment of plants. 



6. Explain how variation and selection are used together in the improvement 



of plants. 



7. Give the elements which a plant breeder must always keep in mind. 



8. Define and illustrate the term "cross" among plants. 



9. Describe one method of artificial pollination and state its use. 



10. On the blackboard, or on a sheet of paper, give a bracket outline of 



results of crossing according to Mendel's law. 



11. What are pedigrees? What is meant by pedigreed corn? 



Reference. Cornell Reading-Courses No. 38, Principles and Methods 

 of Plant Breeding. 

 3 



