548 



INDEX 



Nicotiana rustica 



experimental results, 162-71 



experiments with, 161-62 



fixing transgressive vigor in, 161-74 



plants of, 163 

 Nitrogen metabolism 



of corn and tomato, 107 



of the plant, 110 

 Nitrogen nutrition 



relation of hybrid vigor development, 106 



use by hybrids and inbreds, 106 



Non-allelic interactions, 164, 174 

 Non-heritable variability, 162 

 Non-random segregation at megasporo- 



genesis, 70 

 Normal segregation, 70 

 Northeastern Flint corn of Guatemalan 



origin, 129 

 Northern Flints, 127, 129, 131 



characteristics of, 136 



distribution of chromosome knobs, 130 



historical record, 128 



kernel of, 133 



pairing of rows, 133 



seeds of, 134 



shanks of, 134 



and Southern Dents, crosses between, 137 



and Southern Dents, differences between, 

 136 



typical ears of, 134 



typical plants, tassels, and staminate 

 spikelets of, 135 

 Nuclear membrane and chromosomes, 262 

 Nucleotide cozymase, 110 



Oenothera, 20 



One gene heterosis, 203-15, 217 



One gene-one enzyme hypothesis, 268, 276 



Open-pollinated varieties, continuing im- 

 portance in inbreeding program, 140 

 Outcrossing, 406 



Overdominance, 221, 229, 282, 323, 330, 

 338, 416, 451-73, 492, 497 



in cattle, 467 



equilibrium gene frequency with, 463-64 



physiological nature of, 457 



in tomato hybrids, 319 



in yield of corn, 469 

 Overdominance and dominance, 282-97 

 Overdominance and gene action, 294-96 

 Overdominance and recurrent selection, 



451-73 

 Overdominant loci, 291 

 Overepistasis, 458 



Para-aminobenzoic acid. 111, 207, 210, 214 



Parthenogenesis, 47, 389, 394-99 

 artificial induction, 396 

 effect of male parent, 394 



effect of seed parent, 395 



in monoploid derivatives, 397 



Partial dominance as explanation of hybrid 

 vigor, 65 



Partitioning phenotypic variance, 161 



Partitioning phenotypic variance, herita- 

 bility, and number of effective factors, 

 168-70 



Paternal monoploids, 393 



Penicillin, 269 



Penicillin screening, 272-74 



Performance index, 382, 386 



Performance indices, 284-85 



Permanently viable pure lines, 16 



Phenotype, 336, 344, 463 



Phenotype-genotype relations, 162-65 



Phenotypic and genetic covariances and 



correlations, 515 

 Phenotypic and genie dominance, 318 

 Phenotypic variance, partitioning, 161 

 Phosphorus-absorbing capacity in corn, 107 



Phosphorus nutrition 

 relation of hybrid vigor development, 106 

 use by hybrids and inbreds, 106 

 Photosynthesis, 327 

 Physical vigor, 34 



"Physiological key" substances, 112 

 Physiological mechanism of heterosis, 112 

 Physiological mosaic dominance, 295 

 Physiological nature of overdominance, 457 

 Physiological superiority of heterozygote, 

 158 



Physiology of gene action in hvbrids, 98- 



113 

 Pigeon-dove hybrids, 243-45 

 Plant breeding, selection, 15 

 Plant hybridization, 9 

 first record of, 9 



Plant hybrids, 7-13 



Plasmagenes and chromogenes, 233-34 

 in heterosis, 224-35 



Pleiotropy and interallelic and intraallelic 



interactions, 317-19 

 Pleiotropy and linkage, 317-18 

 Pneumococcal types, specificities of, 254 

 Pneumococci, antigens of, 254 

 Pod corn, 418 

 PodophylUn, 397 

 Pollen abortion, 74 

 Polycross trials, 56 

 Polycrosses, forage yields compared to top 



crosses of the same clones, 57 



Polygenes, 173 



