APPENDIX I 



Polarization {continued) 



3. Of centromeres, the initiation of orientated division during mitotic 

 metaphase. Darlington 1937. 



Pollen Grain, the male gamctophytc in the flowering plants. 



Pollination, the placing of pollen on the receptive stigma of a 

 flower. 



PoLYCENTRic, of a chromosomc or chromatid having several Centromeres. 

 Darlington 1937. 



Polyembryony, the production of more than one embryo within the 

 testa of one seed in a flowering plant, cither from one or several 

 zygotes, extra zygotes being sexual or parthenogenetic, from reduced 

 or unreduced eggs. The extra eggs may be derived from vegetative 

 nucellar cells, sister mother-cells, sister spores or sister nuclei within 

 one embryo-sac. Marchal 1904. 



Polygamy, the system of mating where one male unites with several 

 females (polygyny) or vice versa (polyandry). 



Polygenes, i. Members of a Polygenic System. 



2. Genes whose differences or mutations are too slight to be identified 

 by their individual effects in individuals, and which are therefore 

 presumed to have a small eff*ect on the selective advantage of the 

 individuals. Cf. Major Genes. 



Polygenic Combination, v. Balance. Mather 1941. 



Polygenic System, of genes having eflfects similar and supplementary 

 to one another, and small in comparison with the total variation. 

 The members of such a system are replaceable in their effects. 



Polyhaploid, Haplo-polyploid. Katayama 1935. 



Polymeric Genes, non-allelomorphic genes of apparently identical and 

 cumulative action. Undefmed with regard to individually recog- 

 nizable effect. The Cumulative Factors of Nilsson-Elile. Charac- 

 teristic of allopolyploids. Cf. Polygenes. Two genes of identical but 

 non-cumulative effect are said to be Duplicate. Lang 191 1. 



PoLYMiTOSis, the intercalation of rapid supernumerary mitoses in the life 

 cycle immediately after meiosis, without division of the chromo- 

 somes, Beadle 1933, or with division of the chromosomes. Darlington 

 and Thomas 1941. 



PoLYMORPinsM, the occurrence in the same habitat of two or more 

 distinct forms of a species in such proportions that the rarest of them 

 camiot be supposed to be maintained by recurrent mutation from 

 any other. Ford 1940. In practice the genetic diversity associated with 

 the control of mating is excluded, but Polymorphism may be con- 

 fined to one sex, e.g. Lebistes. 



410 



