8 MENDELISM 



You would probably expect the offspring to be inter- 

 mediate in character between the two parents, but such was 

 never the case. In each instance the offspring exactly 

 resembled one parent, i. e. it showed only one of any pair 

 of contrasted characters possessed by the parents, to the 

 entire exclusion of the other character. 



Thus (Fig. 5) a tall plant crossed with a dwarf produced 

 only tall offspring : e.g. the ordinary tall pea was crossed 

 with the cupid variety, which is only 3 or 4 inches high ; 

 the ripe seeds were sown, and produced only tall 

 plants — 



Coloured flowers crossed with white produced coloured 



flowers only ; 

 A yellow-seeded plant crossed with a green-seeded one 



produced only yellow seeds ; 

 Smooth-seeded crossed with wrinkled-seeded plants gave 



smooth seeds only. 



Thus there was always one of the two contrasted 

 characters in each cross that appeared exclusively in the 

 hybrid offspring, and to this character Mendel applied the 

 term Dominant, while that character which did not appear 

 in the offspring he termed Recessive. 



These two terms ("dominant" and "recessive") you 

 should particularly remember. They are terms for which 

 I am not able to give you any simpler equivalents. You 

 will meet with them repeatedly in the literature of 

 Mendelism. 



As a cross between a tall and a dwarf plant produces 

 only tall offspring, tallness is said to be dominant to 

 dwarfness — 



Coloured flowers are dominant to white flowers ; 

 Yellow seeds are dominant to green seeds ; 

 Smooth seeds are dominant to wrinkled. 



