Reversion —129— Rut 



Reversion. — The reappearance of an ancestral character not 

 exhibited by the immediate parents and which has usually not 

 appeared for several generations. 



Rheogameon (Rassenkreis), — A species composed of seg- 

 ments of reasonably marked morphological divergence whose 

 distributions are such that gene interchange may take place 

 in sequence between them; individuals of contiguous segments 

 are interfertile (Camp & Gilly). 



Riboflavine. — Cj^HgoOgN^, one of the components of the 

 vitamin B^ complex. 



Rings. — (i) At mitosis, chromosomes with no ends, (ii) At 

 meiosis, chromosomes associated end to end in a ring, usually 

 by terminal chiasmata; especially applied to diploid inter- 

 change heterozygotes where more than two chromosomes are 

 so associated (Darlington). 



Rods. — Part of the Golgi apparatus. 



Rogue. — N. A variation from the standard type of a variety 

 or strain. V. To remove variant individuals from a variety, 

 strain, etc. 



Roguing. — The removal of undesirable individuals from a 

 variety in the field. 



Rose End. — The end of a tuber (typically a potato) furthest 

 from the point of attachment. Most of the "eyes" (dormant 

 buds) are at the rose end. 



Rotation (of chiasmata). — The relative rotation of the four 

 "arms" of a bivalent on either side of a chiasma, which often 

 occurs between early diplotene and diakinesis (White). 



Rules, Ecological. — See under Allen, Bergmann, Gloger, 

 Rensch. 



Runner. — A procumbent shoot which takes root, forming a 

 means of vegetative propagation. 



Rut. — The period of sexual activity; oestrus. 



