GREGOR MENDEL 539 
dividuals differing in heritage, and not much can be determined 
concerning the laws of heredity from such a mixture. The 
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 Brinn, 
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 ~ ia 
attributed their failure to Fic. 474.— Gregor Mendel, whose 
reach definite conclusions to theory of inheritance is the most im- 
F portant contribution ever made to our 
a want of precise and con- ieemarlede al heredit 
3 ‘ ¢ y. 
tinued analysis. To obtain : 
definite results he saw that it was necessary 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- 
