As the possession of either character is a matter of 

 chance, on the average 50 per cent, of the germ cells in the 

 hybrid will bear the dominant character and 50 per cent, 

 will bear the recessive character. If we could pick out at 

 random any 100 pollen or male cells to fertilize any 100 egg 

 or female cells we will see that there are equal chances for 

 four results : 



1. A male cell with a dominant character may meet a 



female cell with a dominant character. 



2. A male cell with a dominant character may meet a 



female cell with a recessive character. 



3. A male cell with a recessive character may meet a 



female cell with a dominant character. 



4. A male cell with a recessive character may meet a 



female cell with a recessive character. 



In an abbreviated form the mating may be represented 

 as follows: — 



f D D. 



Male Cells \ ^ Z^-^-----''''.^^ R 



I R ■ ■■ ■•-■■••■ R 



or 1 DD— 2 DR— 1 RR 



Female Cells 



The net result will, therefore, be 25 per cent, pure 

 dominant, 25 per cent, pure recessive, and 50 per cent, im- 

 pure dominant. 



Mendel's Experiments. — Mendel used pure strains of 

 the common garden pea {Pisum sativum) in his memorable 

 experiments which led to the discovery of the laws of in- 

 heritance. Twenty- two varieties or sub-species were se- 

 lected and used during the eight years of experimentation. 

 Seven different characters were chosen and investigated 

 separately : 



1 Cotyledon or 



1. Form of seed — round or wrinkled^ first genera- 



2. Color of endosperm — yellow or green [ tion charac- 



j ters 



3. Color of seed coat — white or grey 



4. Form of pods — soft or hard 



5. Color of unripe pods — green or yellow 



6. Position of flowers — axial or terminal 



7. Length of stem. — tall or dwarf. 



Parental 

 characters 



(1) — Round and wrinkled are termed contrasted characters; likewise 

 yellow and green; white and grey, etc. 



S3 



