32 The Thuud and Fourth Generation 



theories of the origin of species. In 1900 three 

 other investigators, Hugo de Vries, a Hollander, 

 Correns, and Tschermak, working independ- 

 ently, arrived at much the same results that 

 Mendel had reached. In reviewing the litera- 

 ture of the subject de Vries unearthed Mendel's 

 pubhcation, and the later discoverers promptly 

 gave the credit of priority to Gregor Mendel. 

 So the formulated statement of the way in which 

 many characters behave in hereditary trans- 

 mission is still called Mendel's law. 



Some pea vines bear peas that are quite 

 green when ripe, others produce those that are 

 a distinct yellow. Mendel used a plant of each 

 of these two sorts as parents, cross-poUinating 

 them carefully. The process is now accom- 

 plished somewhat in the following way. Just 

 before the flower buds are ready to open, some 

 of them are opened by hand on each sort of 

 vine and the anthers removed. Such blossoms 

 are then powerless to discharge pollen on to 

 their own stigmas. Small paper bags are 

 tied over these flowers so that no other pollen 

 can accidentally get to them by wind or 



