298 BREEDING CROP PLANTS 



Replication. Systematic repetition. Used in field work to designate the 

 systematic distribution of plots of each strain or variety to overcome soil 

 heterogeneity. Two replications means the use of three plots systemati- 

 cally distributed. 



Roguing. The act of removing undesirable individuals from a varietal 

 mixture in the field by hand selection. 



Seed. -The mature ovule, consisting of the kernel and its proper coat. 



Self-fertilization. The union of the egg cell of one individual with the 

 sperm cell of the same individual. 



Self -sterility. That condition in which the male gametes of an organism 

 are incapable of fertilizing the female gametes of the same individual. 



Segregate. With reference to Mendelian unit-characters, to become 

 separated through the independent distribution of the genetic factors 

 before or at the time of the formation of the gametes. 



Sex-linked Inheritance. The association of the determiner for any unit- 

 character with a sex-determiner, in such a manner that the two determiners 

 are either generally included in the same gamete, or that they are generally 

 included in different gametes. 



Somatic Segregation. Segregation during somatic division. 



Species. A group of varieties or a single variety which in botanical 

 characters and genetic relationship can be differentiated from another group 

 or variety belonging to the same genus or to other genera. 



Spikelet. A small or secondary spike, especially in the inflorescence of 

 grasses. 



Spike. A simple inflorescence with the flowers sessile or nearly so on a 

 more or less elongated common axis or rachis. 



Sperm or Sperm Cell. Male sex-cell. 



Standard Deviation. An absolute measurement of variation in terms of 

 the mean. The square root of the sum of the deviations squared divided 

 by the number of variates. 



Sterility. Inability to reproduce; when male and female gametes, through 

 incompatibility or some other cause, are incapable of mating or fertilization. 



Strain. A group within a variety which constantly differs in genetic 

 factors or a single genetic factor difference from other strains of the same 

 variety. 



Tassel. Used to designate the staminate inflorescence of maize. 



Unit-character. In Mendelian inheritance, a character or alternative 

 difference of any kind, which is either present or absent, as a whole, in each 

 individual, and which is capable of becoming associated in new combinations 

 with other unit-characters. 



Variate. -A single magnitude determination of a character. 



Variety. A group of strains or a single strain which by its structural or 

 functional characters can be differentiated from another variety. 



Variety Group. A complex of varieties which resemble each other more 

 than varieties belonging to a different group. Of lower grade than species. 



Xenia. The apparent immediate effect of pollen. It results from 

 double fertilization. 



Zygote. The body formed by the union of two gametes and containing 

 2x number of chromosomes. 



