660 INDEX 
Heterosis in species hybrids, 234 Horses, Suffolk Punch, 460, 466 
in trees, 365 Thoroughbreds, 461 
manifestations of, 353 types of, 460 
utilization in corn, cucumber, tomato and white dominant in, 579 
tobacco, 362 Horticultural practice, bud selection in, 391 
in vegetatively propagated plants, 364 Hoshino, linkage in peas, 125 
Heterosynapsis, 201, 204 Hover, prepotency, 574 
Heterozygosis, and fertility, 559 Hovey, hybridization, 294 
and hybrid vigor, 231 plant breeding, 437 
Heterozygotes, contamination of factors in, 189 strawberry, 289 
number of, in F2, 100 Hume, peach, 297 
Heterozygous genotypes, 72 Humming birds cross tobacco, 319 
number of kinds of, in f2, 100 * Huntington’s chorea, 525 
Heuer, Solanum chimera, 378 Hunt, timothy, 294 
Solanum grafts, 374 Hurst, horses, 465 
Hibiscus, dimorphic leaves, 275 sweet pea, 310 
Hinny, 517 Hutcheson, selection, 339 
sterility of, 556 Hyacinth, improvement by Dutch, 288 
Hippeastrum, hybridized, 438 introduction, 287 
History of animal breeding, 443 species and varicties, 302 
of plant breeding, 287 Hyalodaphnia, 23 
Hoffman, hybridization, 439 Hybrid, first plant, 438 
Hoge, Miss, reduplication of legs in Drosophila, seed corn, producing, 361 
272 Hybrids, aphis resistance in, 410 
supernumerary legs in Drosophila, 136 cavy, 223 
Homeosis due to mutilation, 269 forms of species, 227 
Homeotic variations, 16 graft, 374, 382 
Homosynapsis, 201, 204 increased production in Fy, 353 
Homozygotes, number of, in Fx, 100 intergeneric, 296 
Homozygous genotypes, 72 intermediate expression in, 147 
number of kinds, in Fs, 100 interspecific, 296 
of tobacco, 182 mosaic expression in, 152 
Honey bee, 26 multifactor, 94 
sex-determination, 210 Nicotiana, 228, 229 
Hops, heterosis in, 364 Cnothera, 244 
Hopkins, corn breeding experiments, 327 sterility of, 556 
maize, 293 in species, 234, 236, 238 
Hopkins and Smith, corn experiments, 328 superior qualities in F1, 359 
Hormones and dimorphism, 276 utilization of, in breeding, 353 
Horse, American Standard bred, 484, 495, 574 variable character, expression in, 149 
chromosome number in, 519, 537 vigor of species, 230 
fertility in, 552 Hybridization, 11, 291, 294, 342 
history of modern, 460 and animal breeding, 508 
hybrids, 516, 528 at Svaléf, 425, 427 
-quagga hybrids, 565 begun by Knight, 288 
secondary sexual characters in, 548 castration, 343 
sex-determination in, 536 choice of parents, 343 
spermatozoa in, 541 conditions favorable for, 350 
telegony, 565 difficulties in, 350 
-zebra hybrids, 468, 520, 557, 567, 570 extensive use, 311 
Horses, Arabian, 444, 460, 566, 596 for disease resistance, 408 
Barbs, 444, 460 ‘future promise of, 294, 312, 316, 352 
coat color in, 465 general method, 343 
Clydesdale, 460, 461 Goss and Mendel, 294 
creating a gray breed, 470 harmful effects of, 571 
Danish, 444 in apples, 295 
diversity of ancestry, 460 in birds, 521, 543 
Mendelism in, 465 in cattle, 473, 475, 520, 531, 533, 542 
Percheron, 444, 460 in Coleus, 386, 389 
racing, 496 ; in cotton, 295 
Shetland, 460, 489 in creating varicties, 302, 311 
Shire, 460 in grain breeding, 294 
Standard bred, 465, 467 in guinea-pigs, 223, 235, 542 
sterility in, 552 in horses, 516, 528 
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