Heredity 205 



hybrid dominance, which is twice as frequent as the 

 other, breaks up into constant dominance, hybrid domi- 

 nance, and recessiveness. (3) Mendel's law deals pri- 

 marily with mere characters, not with a variety or with 

 a plant as a whole. Every plant is a composite of a mul- 

 titude of characters, and from the plant-breeder's point 

 of view there may be as many undesirable characters as 

 desirable ones. No plant is perfect; if it were, there 

 would be no need of plant-breeding. The breeders want 

 to preserve the desirable characters or traits and elimi- 

 nate the undesirable ones ; but under the strict interpre- 

 tation of mendelism this may be difficult and perhaps 

 impossible. The one egg gamete and the one sperm 

 gamete that unite to make the new plant, each contains 

 all the alternative parental characters; these various 

 characters appear in the offspring, and all that the breeder 

 gains is a new combination or arrangement of characters, 

 and the undesirable attributes may be as troublesome 

 as before. (4) The breeder usually wants wholly new 

 characters as well as recombinations of old ones, or he 

 wants augmented characters, and these lie outside the 

 true mendelian categories. For example, a carnation 

 grower wants a four-inch flower, but he has only three- 

 inch flowers to work with, and the augmentation of char- 

 acters is no part of the original mendelian law. Perhaps 

 these augmented and new characters are to be got by 

 means of ordinary variation and selection, or other extra- 

 crossing means; but we know, as a matter of fact, that 

 augmented characters do sometimes appear in hybrids. 

 (5) New and unpredictable characters are likely to arise 

 from the influence of environment or other causes, and 



