FLOWERS 193 



Sometimes the offspring combines desirable qualities of both 

 parents, and sometimes undesirable qualities predominate. 



In this way the plant breeder can improve his plants by a careful 

 selection of parent plants and a destruction of those which show 

 undesirable qualities. 



Thus sweet corn and pop corn have been produced from the primi- 

 tive wild field corn of the Indian. 



In recent years the seedless apple and many other new fruits 

 and flowers have been produced by crossing and selection. 



Variation 



Note. Examine a large number of plants of the same sort 

 with a view to their points of difference. The leaves of dandelion 

 plants show very great differences in outline, and those of the arrow- 

 head are so different in form that there are seldom two leaves alike 

 on the same plants (hence the name Sagittaria variabilis) . 



Exercise. Select two plants which show as much dif- 

 ference as possible. The oxeye daisy and Indian corn are 

 good for this purpose. 



(a) The Oxeye Daisy 



Compare the two plants. Are they alike in size? Are 

 the leaves alike in size and shape? Make note of -any dif- 

 ferences in leaf outline. Compare the stems as to thick- 

 ness and strength. Look for differences in habit of growth. 

 Are there any differences in surface characteristics, such as 

 smoothness, roughness, pubescence, etc.? Compare the 

 flowers as to number of heads, size, number of ray flowers 

 to each head, and color and position of the floral parts. Try 

 to find two oxeye daisies which are exactly alike in all these 

 qualities. 



What do you conclude as to absolute likeness among 

 flowers ? 



EXP. BOT. 13 



