266 AGRONOMY 



and female gametes have another chance to pair, and this 

 naturally results in some plants being produced from the 

 pairing of two white gametes, and others from two rejl ones, 

 while still others continue to be mixed as before. The example 

 cited is probably much simpler than is usually the case in 

 nature when a cross is made, since it is concerned with a 

 single character only. It is likely that a similar relationship 

 exists between each pair of contrasting characters in the plants 

 hybridized, one character being dominant and one recessive in 

 the first generation, but both appearing in the second in the 

 proportions indicated. Smooth leaves may be recessive to 

 downy ones, short stems may be dominant over long ones, 

 large flowers dominant over small ones or the reverse. Thus 

 the skillful cultivator is presented the opportunity of varying 

 his plants in many ways by combining the characters differ- 

 ently. It must not be assumed, however, that all plants be- 

 have in the manner outlined in the foregoing. There are some 

 crosses which are more or less perfect blends of the original 

 forms, and others in which the characters do not appear to 

 separate out according to Mendel's law in the succeeding gen- 

 eration. In others certain characters may blend, though the 

 species as a whole behaves according to the law. What these 

 characters are and how they function in crossing is still a sub- 

 ject for investigation. Crossing two forms in which some of 

 the characters are alike may also result in intensifying these 

 characters. 



Selection. Variations of whatever kind merely offer oppor- 

 tunities for plant breeding; they give different plants, not 

 necessarily better ones. The new forms are possibly as fre- 

 quently below a desired standard as above it. Any permanent 

 improvement must be made by careful and wise selection. 

 The gardener practices a certain form of plant breeding, 

 though possibly unconsciously, when he selects seeds from his 

 best plants for producing the next year's crops. To achieve 



