INDEPENDENT MENDELIAN INHERITANCE 69 
When the progeny of these tall hybrid plants were grown three-fourths 
of the plants were tall, like the original tall variety, and one-fourth were 
dwarf, like the original dwarf variety. Although like the tall plant in 
appearance, therefore, the tall hybrid plants which were produced by 
crossing a tall and a dwarf plant displayed their hybrid nature in the 
kind of progeny they produced. To distinguish them from the tall 
parents which produced only tall plants, they are accordingly called 
tall hybrids. Continuing this experiment, Mendel found that the dwarf 
segregants of the second generation bred true, they produced only 
dwarf plants; but of the tall plants one-third only bred true, and the 
other two-thirds proved to be tall hybrids, for three-fourths of their 
progeny were tall plants and one-fourth dwarfs. The progeny of the 
original tall hybrid plants, therefore, when subjected to this analysis 
was found to consist of 1 tall: 2 tall hybrid:1 dwarf. The experimental 
results of the hybridization of tall and dwarf peas may accordingly be 
diagrammed as in Fig. 33. 
Tall x Dwarf 
Tall hybrids 
—_ — 
1 Tall 2 Tall hybrid 1 Dwarf 
Tall 1 Tall 2 Tall hybrid 1 Dwarf = Dwarf. 
i i 
Tall Tall 1 Tall:2 Tall hybrid :1 Dwarf Dwarf Dwarf 
Fic. 33.—Results of hybridization of tall and dwarf peas. 
Mendel studied hybrids involving several different pairs of contrasted 
characters and found that in every case one member of each pair of 
characters was expressed unchanged in the hybrids, whereas the other 
member of the pair became latent and its presence could be detected only 
by growing the progeny of the hybrid. Those characters which were 
expressed unchanged in the hybrid Mendel termed dominant, the latent 
characters he called recessive. In the above experiment, for example, 
tallness was dominant and dwarfness, recessive. Mendel saw that the 
dominant character, therefore, in these experiments possessed a double 
significance, that of parental character in which case a uniform progeny 
of dominants is produced and that of a hybrid character in which case 
one-fourth of the offspring display the contrasted recessive character. 
In the above experiment the parental dominants are the tall parents and 
the hybrid dominants are the tall hybrids. The condition of dominance 
for a character, therefore, is determined by the fact that in the hybrid 
that character is expressed to the exclusion of its contrasted character. 
Dominance is by no means a universal phenomenon, but in Mendel’s 
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