1 62 MAIZE 



;hap. tion when fully understood. In our experience, as reported 

 v - here, no exceptions to Mendelian interpretation have been found. 

 Such exceptions may exist, yet it seems as unwise to say that 

 Mendel's Law is not general as to conclude at once that it 

 can be made to cover every possible case. One may say that 

 Mendel's Law has covered so many cases that its generality is 

 rendered highly probable, although insufficient genetic investi- 

 gation has been accomplished to place it on equal terms with 

 any of the great laws of physics and chemistry. Yet some of 

 the great laws of chemistry were accepted when surrounded 

 by seeming exceptions. Some of these exceptions have been 

 cleared up by such recent advances as the Ionic Theory and 

 the Phase Rule ; some still remain. 



"Is it not probable that other like generalities will be 

 found in biology, which, although they may entirely change 

 our general conception of the fundamental action of Mendel's 

 Laws, will nevertheless leave the facts upon which it was 

 based as useful and practicable as have been left the facts of 

 chemical recombination in definite and multiple proportions, in 

 the light of the Electron Theory" (East and Hayes, i). 



123. Reproduction and Transmission of Characters. — As 

 already explained f' 11 74, JJ, and 78) the higher types 

 of plants, like animals, bear male and female organs of 

 reproduction, and the formation of a new maize plant 

 depends on the fertilization of a female cell by a male 

 cell. Reproduction is effected by the union of the nucleus 

 of the pollen grain (H 78) of the male flower with the nucleus 

 of the egg-cell in the ovule of the female flower. These sexual 

 cells, viz., the pollen grain and the egg-cell, are known as 

 gametes or " marrying cells ". By the fusion of the nuclei of 

 the gametes a new cell is formed, known as the zygote. The 

 zygote gives rise — by repeated cell-division, called somatic 

 division — to the complete adult plant, bearing new germ-cells, 

 which subsequently ripen into gametes, thus completing the 

 life-cycle of the plant. 



Since the gametes are the only connecting link between 

 successive generations, each gamete carries the power of repro- 

 ducing the parental characters. If the parents are alike, and 

 are pure-bred ' (% 125), the progeny will be like them. Selection 

 in breeding is based on the principle that anion between two of 

 a kind produces the same kind, provided the strain is pure. 



