THE SCIENCE OF BOTANY 7 



important facts of plant physiology thus became established. 

 Since that time the development of modern chemistry and 

 physics has made possible a steady advance in our knowledge of 

 the physiological processes of living things. 



The publication of the "Origin of Species" by Charles Darwin 

 (Fig. 3) in 1859 resulted in a general acceptance among scientists 

 of the theory of evolution. A recognition of the fact that the 



Fig. 3.— Charles Darwin, 1809-1882. 



plants of today have been slowly developed from simpler ancestors 

 has had a profound effect upon botanical science and has stimu- 

 lated a great interest in reconstructing the "family tree" of the 

 plant kingdom and establishing a really "natural" system of 

 classification, based on actual relationship, to replace the artificial 

 systems of Linnaeus and his predecessors. It has led also to a 

 more intensive study of the laws of variation and inheritance, and 

 the causes and method of evolution. This has been encouraged 

 still further by the discovery of Mendel's Law of Inheritance, 

 propounded in 1866, disregarded for many years, and finally 

 brought to the attention of biologists again in 1900. 



The present state of the science of botany, then, is the result 

 of a long period of slow development, in which truth has been 

 gradually separated from error and our present vast store of facts 

 amassed. With each advance, new questions have arisen and 

 new fields of investigation have opened, until the science has 



