58 TEXTBOOK OF BOTANY 



ture and development that result from them. If these changes did not 

 result in the death of the organism, the plant survived and the altera- 

 tions v^^ere transmitted to the offspring. Such alterations in protoplasm 

 and their transmission from one generation to another are discussed 

 in the chapters on chromosomes, heredity, and variation. 



Summary. Man seems always to have felt an urge to account for him- 

 self and for his surroundings. Perhaps this urge had its origin in the 

 fear of the unknown rather than in the intelligent curiosity that incites 

 the student of modern times. Until man began to apprehend the proc- 

 esses of nature and to perceive the consequences of one process in 

 relation to another, there could be no scientific approach to interpreta- 

 tion. The myths that had grown up about the objects and processes of 

 the physical world had to be replaced by facts and interpretations in 

 accord with the general principle that what happens is a consequence 

 of preceding events without reference to future needs or purposes. In 

 the interpretation of the biological world on the basis of the principle of 

 causality, progress has been comparatively slow. Personification of plants 

 and animals is still chosen by manv writers as the basis of interpreting 

 biological phenomena. Only the more thoughtful ones are skeptical of 

 interpretations that ascribe conscious effort to all sorts of living organ- 

 isms. Slowly during the last centurv, and much more rapidly during the 

 present one, biologists have paved the way for a more intelligent inter- 

 pretation of biological phenomena. The work of all our biological re- 

 search institutions is directed toward the discovery of the facts and inter- 

 dependence of biological processes. Perhaps the greatest need today is 

 that the average citizen should become as intelligently conscious of 

 advances that have been made in the scientific interpretation of his 

 biological environment as he is of those of his physical and chemical 

 world. This chapter emphasizes the importance of clearly recognizing 

 the different points of view from which interpretations of plant behavior 

 are made. 



