PLANT BREEDING AND EVOLUTION 185 



Gregor Mendel was an Austrian monk who in 1865 began 

 experiments on heredity in the gardens connected with the mon- 

 astery at Briinn, Austria. He experimented on peas, and in his 

 studies he selected only certain easily recognizable characters for 

 observation in his experimental plants. Some of these characters 

 related to the seeds, such as seed color, the smobth or wrinkled 

 character of the seed coat, and the sizes of seeds; tallness and 

 shortness of stems and hairiness and smoothness in leaves were 

 other characters relating to the plant body which Mendel selected 

 for observation. 



Mendel 's method of observing a few characters only, instead 

 of attempting to observe all the characters in the plants under 

 observation, is the most distinctive feature of his work. It 

 marked a new epoch in the study of heredity, the importance 

 of which we can hardly overestimate. When he crossed two 

 parents which possessed such definite contrasting characters 

 as tall and short stems, or smooth and wrinkled seeds, Mendel 

 found that the appearance of these characters in the offspring 

 followed definite laws, or principles. These laws, or princi- 

 ples, which are now called Mendel's principles of heredity, 

 may be illustrated by giving Mendel's results, obtained in an 

 experiment with seed characters in peas. Mendel chose peas 

 because they are self-pollinating, so that it was unnecessary 

 to pollinate the stigmas artificially where self-pollination was 

 desired. In the experiment illustrated in Fig. 96 he chose 

 two pure strains of peas, which he had previously tested as to 

 their purity. In one of these strains, used as either a male or a 

 female parent in the experiment, the seeds were all smooth and 

 round ($$), while in the other parent the seeds were all wrinkled 

 (ww). When plants grown from these parent seeds were cross- 

 pollinated artificially, the seeds thus produced were all smooth 

 like one parent. Since, however, these hybrid children (Sw) had 

 received both the smooth and the wrinkled character from the 

 two parents, Mendel concluded that the character in the germ 

 which determined the smoothness of the seeds was dominant over 

 the wrinkling character. He therefore called the smooth char- 

 acter dominant and the wrinkling character latent or recessive. 



