Knight — 132 — Dictionary 



Scrub. — (i) An animal of mongrel breeding belonging to no 

 definite type, (ii) A low grade individual. 



Secondary Association. — The side-by-side association of 

 bivalent chromosomes at meiosis. 



Secondary Kinetochore. — A secondary centre of attraction 

 in addition to the normal centromere. See T-chromosome. 



Secondary Mutant. — Secondary trisomic. See Trisomic. 



Secondary Nucleus. — The nucleus resulting from the fusion 

 of the two polar nuclei in the embryo-sac. 



Secondary Pairing. — Secondary Association, q.v. 



Secondary Polyploid. — An allopolyploid in which some of 

 the chromosomes in the basic set occur more frequently than 

 others (Crane & Lawrence). 



Secondary Segregation. — The segregation in an allopolyploid 

 of differences between its ultimate diploid parents (Darling- 

 ton). 



Secondary Sexual Character. — A character without direct 

 reproductive function whose expression is controlled by sex 

 hormones. 



Sectional Hyperploidy. — The state of having one segment 

 of a chromosome present both as part of the normal comple- 

 ment and, in addition, as a separate chromosome or as part 

 of a non-homologous chromosome (as a result of transloca- 

 tion) ; hyperdiploidy. 



Sectorial Chimaera. — A plant with a deeply seated sector of 

 genetically distinct tissue (Crane & Lawrence). 



Secundines. — (pl.)« The after-birth. 



Seed, Elite. — Seed used for carrying on a special selected 

 line from which stock seed will subsequently normally be 

 produced. Extra-pure seed. 



Seed Generation (S.G.). — S.G. 1 represents the first seed 

 generation i.e. seed directly produced by cross-pollination and 

 from which Fj plants will grow; S.G. 2 represents self-bred 

 seed from an Fj^ — the second seed generation ; S.G. 3, the 

 third seed generation, is self-bred seed from an F^, etc. 



Seed, Stock. — Seed which is used by the seedsman to sow 

 for the immediate production of commercial seed. 



Segment. — Any given portion of a chromosome. 



Segmental Interchange. — Mutual translocation ; an exchange 

 of non-homologous segments as between two chromosomes. 



Segmentation Nucleus. — The fused gametic nuclei in a 

 zygote. 



