MENDEL'S PROCEDURE ILLUSTRATED 541 



enclosed by the keel that cross-pollination seldom occurs unless 

 it is done artificially. Also there are many varieties of the 

 Garden Pea differing strikingly in color of flowers, height of 

 stem, shape of pod, color of seed coat, and so on. This plant is 

 also easily grown in cultivation and matures in a short time. 



Mendel's discoveries in regard to the distribution of inherited 

 characters throughout successive generations and his explanation 

 accounting for the distribution of characters in a certain way in 

 the offspring constitute Mendel's law. This law he published in 

 1865, but it received no recognition until 1900, at which time 

 its importance was recognized simultaneously by De Vries, 

 Correns, and Tschermak. Since 1900, Mendelism has been the 

 basis for practically all investigations of heredity, and the study 

 of heredity according to the pedigree culture method, as intro- 

 duced by Mendel, we now call genetics. An illustration will make 

 clear the method Mendel used in investigating heredity. 



MendePs procedure illustrated. Mendel's method of inves- 

 tigating heredity may be shown by describing his experiments 

 with tall and dwarf Peas. A tall Pea, having a height, 6 to 7 

 feet was crossed with a dwarf Pea, having a height f to H 

 feet. By means of forceps or other instruments and before the 

 flowers were open, the anthers were removed from the flowers of 

 the plant selected as the mother plant and pollen from the pollen 

 parent was applied to the stigma. The hybrid seeds developed 

 by the mother plant as a result of the crossing were carefully 

 collected. These cross-bred seeds were planted and produced 

 the first hybrid generation of plants, known as the F l generation 

 in our modern terminology. The height of each individual of this 

 generation was carefully noted, and each individual was compared 

 with the parents in respect to tallness or dwarf ness. The 

 individuals of this generation were allowed to self-fertilize, and 

 the seeds of each individual were collected and planted separately. 

 From these seeds he grew the second generation or F 2 generation 

 according to modern terminology. The individuals of this 

 generation were carefully compared with each other, with their 

 parents, and with their grandparents in respect to tallness and 

 dwarf ness and the facts carefully recorded. The individuals of 

 the F 2 generation were allowed to self-fertilize, and from the 

 seeds obtained the F 3 generation was grown, and the individuals 

 in this generation were studied in the same careful way as those 



