296 BREEDING CROP PLANTS 



Heredity. The distribution of genotypic elements of ancestors among 

 the descendants; the resemblance of an organism to its parents and other 

 ancestors with respect to genotypic constitution. 



Heterozygosity. The condition of an organism due to the fact that it is a 

 heterozygote; the state of being heterozygous; the extent to which an indivi- 

 dual is heterozygous. 



Heterozygote. A zygotic individual in which any given genetic factor 

 has been derived from only one of the two generating gametes. Both eggs 

 and sperms produced by such an individual are typically of two kinds, half 

 of them containing the gene in question, the rest lacking this gene; conse- 

 quently the offspring of heterozygotes usually consist of a diversity of 

 individuals, some of which possess the corresponding character while others 

 lack it. 



Heterozygous. The state or condition found in a heterozygote. 



Heterosis. The increased growth stimulus often exhibited in the Fj 

 generation of a cross. 



Homozygosis. The state of being homozygous; the extent to which an 

 individual is homozygous. 



Homozygote. An individual in which any given genetic factor is doubly 

 present, due usually to the fact that the two gametes which gave rise to this 

 individual were alike with respect to the determiner in question. Such an 

 individual, having been formed by the union of like gametes, in turn gener- 

 ally produces gametes of only one kind with respect to the given character, 

 thus giving rise to offspring which are, in this regard, like the parents; 

 in other words, homozygotes usually "breed true." A" positive "homozy- 

 gote with respect to any character contains a pair of determiners for that 

 character, while a "negative" homozygote lacks this pair of determiners. 



Homozygous. The state or condition found in a homozygote. 



Hybrids. The progeny of a cross-fertilization of parents belonging to 

 different genotypes. 



Hull. A term applied to include the lemma and palea when they remain 

 attached to the caryopsis after thrashing. 



Hypostasis. That relation of a gene in which its usual reaction fails to 

 appear because of the masking or inhibitory effect of another gene; con- 

 trasted with "epistasis." 



Inflorescence. The flowering part of a plant. 



Keel. A central ridge resembling the keel of a boat, as in the glumes of 

 some grasses, etc. ; also the inferior petal in the legume flowers. 



Kernel. Matured body of an ovule; seed minus its coats. 



Lethal. A genetic condition causing death. 



Linkage. The type of inheritance in which the factors tend to remain 

 together in the general process of segregation. 



Lodicule. A minute scale at the base of the ovary opposite the palea in 

 grasses, usually two in number, and probably representing the reduced 

 perianth. 



Mean. The arithmetical average. 



Mode. The class of greatest frequency. 



Mendelize. To follow Mendel's law of inheritance. 



Multiple Allelomorphs. Three or more characters which are so related 

 that they are mutually allelomorphic in inheritance. 



