FACTORS OF ORGANIC EVOLUTION. 475 



Now, this is merely a gratuitous aud ad captandum species of argu- 

 ment, one which is designed to please the fancy and to satisfy those 

 superficial spirits who are still determined to read the element of design 

 into organic nature. It does not account for the facts. These particu 

 lar attributes of plants are specialized features, and it is always unsafe 

 to generalize upon specializations. Each and every one of such spe- 

 cialized features must be investigated for itself. Probably the greater 

 number of spinous processes will be found to be the residua following 

 the contraction of the plant body; others are no doubt mere correla- 

 tives of the evolution of other attributes; and some may be the erup- 

 tions of the growth force; and the acrid and poisonous properties are 

 quite as likely to be wholly secondary and useless features. The attempt 

 to find a definite immediate use and office for every attribute in the 

 creation is superficial and pernicious. There are many attributes of 

 organisms which are not only useless, but positively dangerous to the 

 possessor, and they can be understood only as one studies them in con- 

 nection with the long and eventful history of the line of ascent. 



The thought which I Avant to leave with you, therefore, is that unlike- 

 nesses are the greatest facts in the organic creation. These uulikeuesses 

 in plants are (1) the expressions of the ever-changing environmental 

 conditions in which plants grow, and of the incidental stimuli to which 

 they are exposed; (2) the result of the force of mere growth; (3) the 

 outcome of sexual mixing. They survive because they are unlike, 

 and thereby enter fields of least competition. The possibility of the 

 entire tragic evolution lay in the plasticity of the original life-plasma. 

 The plastic creation has grown into its own needs day by day and age 

 by age, and it is now just what it has been obliged to be. It could 

 have been nothing else. 



