APPENDIX I 



Heterostyly, the division of a species into individuals of two (distylic) 

 or three (tristyhc) kinds, distinguished by the relative positions of 

 stigma (ta) and anthers. The expression of Heteromorphic Incompat- 

 ibility. In distylic species the long-styled form is Pin and the 

 short-styled form is Thrum. 



Heterothally, haploid Incompatibility in Thallophyta. Blakeslee 1904. 



Heterozygote, a zygote derived from the union of gametes dissimilar 

 in respect of the quahty, quantity or arrangement of their genes. 

 Usually used in respect of particular gene differences. Batcson 1902. 

 Complex Heterozygote, one whose gametes have numerous differences 



which segregate as a unit. Rentier 19 17. 

 Sex Heterozygote, a zygote of the Heterogametic Sex. A form of 

 Complex Heterozygote. 



Heterozygous, of a heterozygote. Batcson 1902. 

 Heterozygous Sex, Heterogametic Sex. 



Hexaploid, v. Polyploid. 



Hexasomic, v. Polysomic. 



HoMOEOSis (Heteromorphosis), the alteration of one organ of a seg- 

 mental or homologous series from its own characteristic forms to 

 that of some other member of the series. Bateson 1894. 



Homogametic Sex, producing gametes of one kind in regard to their 

 properties of sex determination. Wilson 1910. 



HoMOGENic, of I. a population or 2. a gamete, containing only one 

 allelomorph of a particular gene or genes, or for all genes. Cf. 

 Heterogenic. 



Homologous Variation, Law of, that related species show similar 

 variation owing to mutation in homologous. genes. Vavilov igiz. 



Homology, the similarity of structures in the same or different organisms 

 which they owe to relationship of development or descent. Owen 

 1840. 

 Homology of Chromosomes, applied to whole chromosomes or parts 

 of chromosomes so far as their pairing at meiosis or their visible 

 structure permits them to be regarded as units. Recessive variants 

 enable us to use F^ as the test of homology in action of the chromo- 

 some, as reflecting its constituent genes, while they enable us to use 

 the Fg as a test of homology in position of these genes. 



Homothally, the absence of Incompatibility within species of the 

 Thallophyta. Cf. Heterothally. Blakeslee 1904. 



Homozygote, a zygote derived from the union of gametes identical 

 in respect of the quality, quantity and arrangement of their genes, 

 or of certain of them, Bateson 1902. 



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