GREGOR MENDEL 



539 



dividuals differing in heritage, and not much can l)e determined 

 concerning the laws of lieredity from such a mixture. Tlie 

 average means nothing unless the individuals measured or 

 counted are alike in their heritage, and the only way to be sure 

 that the individuals of a mass or population are homogeneous in 

 constitution is to pedigree them, that is, grow them all from a 

 common stock. The importance of pedigree cultures is well 

 shown in Mendel's work. 



Gregor Mendel. — Gregor Mendel (1822-1884) {Fig. 474), 

 was an Austrian monk and abbott in the monastery of Briinn, 

 where he conducted his ex- 

 periments in the Cloister 

 Garden. He loved plants 

 and loved to experiment with 

 them. Although he studied 

 heredity only as a pastime, 

 his laws of heredity and his 

 experimental method of in- 

 vestigating them are two of 

 the most important contribu- 

 tions ever made to biological 

 science. 



Mendel's success was due to 

 the clearness with which he 

 thought out the problem. He 

 knew the works of other in- 

 vestigators of heredity, and 

 attributed their failure to 

 reach definite conclusions to 

 a want of precise and con- 

 tinued analysis. To obtain 

 definite results he saw that it was necessarj^ to start with pure 

 material, to consider each character separately, and to keep the 

 different generations distinctly separate. He also realized that 

 the progeny of each individual must be recorded separately. 

 Such ideas were new in Mendel's time, but he felt certain that 

 experiments carried on in this systematic way would give regu- 

 lar results and lead to definite conclusions. 



Mendel saw that most could be accomplished by crossing 

 plants of different varieties or species and observing the be- 



FiG. 474. — Gregor Mendel, whose 

 theory of inheritance is the most im- 

 portant contribution ever made to our 

 knowledge of heredity. 



