PLANT EVOLUTION 241 



the part of many people, especially the theologians, who believed 

 that his theories eliminated Deity. In fact, Darwin's theories 

 did not eliminate Deity, but they did emphasize the importance 

 of natural laws. However, his theories were accepted by many 

 scientists and eventually by educated people very generally. The 

 principles of organic evolution as set forth by Darwin have had 

 a more far-reaching influence than those of any other scientific 

 worker. Darwin and his immediate followers were observers of 

 nature rather than experimenters, but in 

 a very few years there arose a school O'l 

 workers who insisted on proving or dis- 

 proving theories by experimental evidence. 

 This method has now spread to practically 

 all branches of the biological sciences. 



Mendel. — Johann Gregor Mendel 

 (Fig. 110) is a name well known to the 

 students of heredity in plant and animal 

 life. He was an Austrian monk who was 

 interested in the breeding of plants and Mendel. 'cProm^Ga'ger's 



Fundamentals of Botany. ) 



worked out certain laws oi heredity which 

 bear his name. His results were published in an obscure publi- 

 cation about 1865 and did not attract attention until about 1900, 

 when they were brought to light by Correns, DeVries and 

 Tschermak. They have had a very decided influence on the study 

 of evolution. Mendel's work was primarily with peas, in which 

 he always studied the inheritance of two contrasting characte^rs. 

 Two plants with contrasting characters (such as long and short 

 plants, smooth and wrinkled seeds, gray or brown seed coats, 

 yellow or green cotyledons) were selected and oros&-pollinated. 

 The seeds were carefully collected and planted throughout a 



