540 



INDEX 



Depletion mutation, 261 



Detasseling, 15 



Deterioration, 16 



De Vries' mutation theory, 20 



Diakinesis, 69 



in heterozygous plants, 68 



Dianthus hybrid, 9 



Dicentric chromatid, 77, 78 



Differentiation, 260 



Diploid behavior at meiosis, 500 



Diploid heterozygote, 202 



Diploids, 389 



Direct tetrad analysis, 258-59 



Disjoining monads, types, 76 



Dispersed heterosis, 127 



Divergent alleles, 173, 458 



cumulative action of, 282 



interaction between, 234 



Divergent spindles, 74 



Domestic f ow 1 hybrids, 245-46 



Dominance, 11, 100, lOl, 167, 284, 332, 

 338, 350, 353 

 to account for heterosis, 350 

 analvsis of, 495 

 complete, 288, 416, 497 

 degree of, 336, 494 

 as explanation of hybrid vigor, 65 

 of growth factors, 60 

 and heterosis, 307, 494-516 

 incomplete, 416 

 by interference, 458 

 in maize X teosinte, 188-92 

 andover dominance, 282-97 

 partial, 65, 497 

 phenotypic and genie, 318 

 and scales of measurement, 306, 313 

 in self-pollinated plants, 166 

 of tomato hybrids, 308 



Dominance of genes, estimation of, 494-516 



Dominance and heterosis as expression of 

 same phvsiological genetic phenomena, 

 307, 309 



Dominance hypothesis, 230, 284 

 objections to, 285 



Dominance of linked genes hypothesis, 282 



Dominant alleles, 101 



Dominant, deleterious, 323 



Dominant favorable genes, 451 



Dominant gene effects, 165 



Dominant genes, 225-26 



Dominant and recessive lethals, 160 



Dominant unfavorable genes, 226-27 



"Double-cross," 40, 42, 43, 166-68 



Double cross hybrids, 433, 444 



Double cross yields versus single cross 

 yields, 58 



Double fertilization, 9 

 and embryo development, 87 

 and endosperm development, 87 

 and growth in the integuments, 87 



Drosophila melanogaster 

 hybrid vigor in, 474-93 

 egg production, 474, 476 

 egg production curve, 476 

 lifetime daily egg production of different 



races, 477 

 races, variation in egg production and 



duration of life, 476 



Drought resistance, in maize X teosinte, 



196-97 

 Dwarf races, growth rates, 121 

 Dwarfs, 62 

 Dyads, 75 



Early testing, 402-11 

 limitations, 406-11 

 as a measure of combining ability, 410 



Early testing and recurrent selection, 400- 

 417 

 results, 403-6 

 as a tool in a breeding program, 406 



Ear-row planting, 22 



Ear-row selection, 456 



Edwards technique of growing auxotrophic 



mutants, 279 

 Effective factor, 298 



Egg production, 478 



distribution of variance, 486 



range, 485 

 Eight-way combinations, 44 

 Elementary strains, 24 

 Elite germ plasm hypothesis, 138-39 

 Embryo development, 104 

 Embryo growth, lag phase, 82 

 Embryo and seed development, 103-5 

 Embryo size as related to seed size and 

 heterosis, 103-4 



Embrj'os 



artificial methods of cultivating, 95 



of barley, 97 



development in inbred and hybrid corn, 

 104 



early growth in relation to endosperm 

 size, 91 



frequency of formation, 95-96 



growing small excised, 96 



growth rates, 87 



vigor, 94 



Endogamy, 5 



Endosperm, 81 



genetic characteristics of triploid condi- 

 tion of the nuclei, 84 

 growth rates, 87 

 heterozygosis, 84 

 hybrid vigor, 85 



