GENETICS AND EVOLUTION 649 
showed only one of the characters occurring in the parental 
plants. The obvious character he termed “dominant,” the 
hidden or latent character, “recessive.”? In one of his experi- 
ments, he crossed tall pea plants with dwarf pea plants by trans- 
ferring the pollen from the anthers of the tall plant to the stigma 
of a dwarf plant; the seeds resulting grew to be tall plants like the 
tall parent. ‘These offspring plants represented the first hybrid 
generation called the first filial generation and are represented by 
the symbol F;. Accordingly, Mendel designated tallness the 
dominant character and dwarfness the recessive character. -He 
next permitted the tall Fi: hybrids to be self fertilized and their. 
offspring called the second filial generation (F2) were found to be 
tall and dwarf in the ratio of three tall to one dwarf. With seed 
obtained from self fertilized /, plants he grew an F3 generation. 
He found that all the dwarfs (recessives) of the F2 when so inbred, 
gave only dwarfs which bred true indefinitely, while all the tall 
plants of the F, generation, when inbred, proved to be of two 
_kinds, one-third pure dominant talls which bred true indefinitely, 
and two-thirds hybrids similar in number of kinds and ratio to 
that obtained by growing seed of F; plants, 7.e., three dominants to 
one recessive. ‘These results may be diagrammatically repre- 
sented as follows: 
PARENTS TxD 
F, (first filial hybrid generation) rae (all tall) 
F, (second filial generation) 1 TT: 27(D): DD (3 tallto 1 dwarf) 
| ; 
F; (third filial generation) All 7 37 1D All D 
When there is only one pair of contrasting characters usually 
but two types of offspring occur in the Fz generation, dominants 
and recessives. 
REsuLts oF Crossinc INDIVIDUALS wiTH Two Pairs 
oF CONTRASTING CHARACTERS 
Dihybrids are individuals whose parents differ in respect to 
two pairs of contrasting characters. When Mendel set out to 
prove the phenomenon of a 3 to 1 ratio in the number of domi- 
