I.] ADAPTIVE FEATURES — SUMMARY. 53 



of parasitic fungi, which appear to be indifferent to all 

 protective contrivances exhibited by plants, nearly 

 every plant supporting one or more of these minute 

 pests, the effects of which will be realized by mentioning 

 the potato disease, 'rust' and 'smut' in the various 

 cereals, and the hop disease, all due to parasitic fungi." 

 Now, this is merely a gratuitous and ad captandum 

 species of argument — one which is suited to please the 

 fancy, and to satisfy those persons who are still de- 

 termined to read the element of proximate design into 

 organic nature. It does not account for the facts. 

 These particular attributes of plants are specialized 

 features, and it is always unsafe to generalize upon 

 specializations. Each and every one of such specialized 

 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 correlatives of the evo- 

 lution of other attributes, and some may be eruptions 

 caused by 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 imme- 

 diate use and office for every attribute in the creation 

 is unphilosophical. There are many attributes of 

 organisms which are not only useless but positively 

 dangerous to the possessor, and they can be under- 

 stood only as one studies them in connection with the 

 long and eventful history of the line of ascent. 



The thought which I want to leave with you, there- 

 fore, is that unlikenesses are the greatest facts in the 

 organic creation. These unlikenesses in plants are (1) 

 the expressions of the ever-changing environmental 



