Knight — 92 — Dictionary 



Male Pronucleus. — The generative nucleus of a male gamete. 



Mantle Fibres. — Spindle fibres; fibres which appear to con- 

 nect the centromeres to the poles of the spindle during cell 

 division. These are possibly artefacts of fixation which corre- 

 spond positionally with some latent 'structure' of the spindle 

 cytoplasm but which do not exist as definite fibres until 

 coagulated by chemical reagents. 



Mass Mutation. — A sudden marked spurt of mutability in 

 a population. 



Mass-pedigree Selection. — A form of mass selection in which 

 individual plants are selected when conditions favour selection 

 for a given character ; selection in the following season may be 

 of individual plants or of complete progenies, according to the 

 seasonal conditions. In the following year the selections are 

 all sown in bulk. 



Mass Selection. — A form of breeding in which individuals, 

 chosen for certain characteristics, are bulked together in the 

 following generation. 



Matched S Gene. — Any S gene (q.v.) which is represented in 

 both the style and pollen in a given polHnation (Lewis). 



Maternal Inheritance. — Inheritance from mother to offspring 

 unaffected by inheritance from the father (J. Heredity). 



Matriclinous. — Matroclinous, q.v. 



Matrix. — The peripheral more stainable portion of a chromo- 

 some. 



Matroclinal Inheritance. — Inheritance in which the offspring 

 resembles the female parent more closely than the male. 0pp. 

 Patroclinal. 



Matroclinic, Matroclinal. — Matroclinous, q.v. 



Matroclinous. — Matriclinous; resembling the mother more 

 closely than the father. 0pp. Patroclinous, Patriclinous. 



Matromorphic. — Similar in appearance to the female parent. 



Maturation. — (i) The formation of gametes by meiosis. 

 (ii) The period which elapses between pollination and the 

 ripening of the fruit. 



Maturation Division. — A form of nuclear division in which 

 the chromosome complement of the nuclei is reduced from the 

 diploid (2n) number to the haploid (n). See Meiosis, 



Mature-plant Resistance. — A term applied particularly to 

 resistance to stem rust in the stages from heading to maturity 

 where this resistance is not correlated with seedling reaction 

 (Hayes & Immer). 



M-chromosome. — (i) A chromosome with a median or sub- 

 median centromere, (ii) A micro-chromosome. 



