Knight — 96 — Dictionary 



Microchromosomic Chromocentra. — The heterochromatin 

 on either side of the centric constriction. 



Microconjugant. — Microgamete, q.v. 



Micro-evolution. — (i) The evolutionary process as con- 

 sidered over short periods of time and limited to small 'groups' 

 of organisms, (ii) Used by Goldschmidt to denote evolution 

 which is dependent on gene mutation and recombination, as 

 opposed to macro-evolution, q.v. 



Microgamete. — The smaller of two conjugants; the male 

 gamete. 0pp. Macrogamete. 



Micro-grafting. — A method by which small embryos, either 

 from artificial cultures or from mature seeds, may be grafted 

 onto normal stocks with protection against evaporation (c/. 

 Blakeslee). 



Microheterochromatic. — An individual or species which dif- 

 fers from its group in having less heterochromatin. 



Micro-mutation. — A mutation, or sudden heritable change, 

 at a single gene locus. 



Micron. — 0.001 mm. 



Micronucleus. — The small reproductive nucleus of many Pro- 

 tozoa as distinct from the large vegetative nucleus or macro- 

 nucleus. 



Micropyle. — (i) The aperture through which the pollen-tube 

 penetrates the ovule, (ii) The aperture in the membrane of 

 the tgg through which the sperm usually penetrates the ovum. 



Micropyrenic. — (i) Having nuclei which are considerably 

 smaller than the average for the species (or individual, etc.). 

 (ii) An individual of this type. 



Microspecies. — A small species or Jordanon. 



Microsphere. — The centrosome, q.v. 



Microsporangia. — Pollen-sacs. 



Microspore. — The haploid cell from which a single pollen 

 grain develops. See Microsporocyte. 



Microsporocyte. — Pollen Mother-cell; the cell which under- 

 goes two meiotic divisions to produce four microspores. 



Micton. — A species of wide distribution, the results of hy- 

 bridization between individuals of two or more species; all 

 individuals are interfertile with themselves and with the an- 

 cestral genotype (Camp & Gilly). 



Mid-body. — The first stage in the formation of a cell-wall 

 between daughter cells; the cell plate. 



Middle Piece. — A vague term signifying the middle region 

 of a sperm. 



Millimicron. — 0.000001 mm. 



