THE EVOLUTION OF PLANTS 51 



pear a variety or mutation which can meet the habitat on its new 

 terms. 



Since the fossil record shows a progressive reversion to simplicity 

 in life forms as we travel back through the ages, it is logical to arrive 

 finally at the single cell as the original home of life. Similarly, pro- 

 jecting life forward, we would expect increasing complexity in the 

 future. This complexity may perhaps be of a social rather than an 

 individual nature. As the total environment becomes more highly 

 developed, life tends to keep pace. If environment regresses, life, 

 too, MUST regress. There are countless examples of such regression. 

 Look at any wornout farm. 



In natural selection the unfit are weeded out by competition or 

 by the development of an unfavorable environment. In human so- 

 ciety, science and brotherly love have enabled many of the physi- 

 cally unfit to survive; the competition is now partly economic and 

 social, and the unfit in these fields go to the bottom of the heap. 

 Even this selectivity is being partially overcome by education and 

 by labor organization. The individual is being protected more and 

 more against social and economic discomforts, and great groups of 

 people are competing against each other for favored situations. Yet, 

 with all his contention, individually and in groups, man tends to 

 ignore the great determiner of his well-being, the maintainence of 

 a healthy, well-balanced natural theatre of operations, the landscape. 



That accidental mutations and variations in the plant and ani- 

 mal world have not been unusual is attested by the 300,000 kinds of 

 plants and 1,000,000 kinds of animals (mostly insects) existing to- 

 day. Add to these the known extinct species and the unknown 

 myriads which have passed from the scene without leaving a yet 

 discovered trace. "While there is plenty of argument as to the rela- 

 tion of mutations to survival and as to what effect environment has 

 in bringing them about, it is fairly certain that numberless new 

 varieties of life have perished because they needed a better environ- 

 ment than was available. But as soils, for instance, improved, varie- 

 ties of plants sooner or later occurred which took advantage of 

 them. In time these became new species. On the earth as a whole 

 there are today probably conditions of topography, soil, and climate 

 which could support most of the forms of life which have ever 

 occurred. In smaller areas, conditions have changed so radically 

 from time to time that many species were wiped out, particularly if 

 their means of dispersal, of migrating into suitable territory, was 

 blocked by topography (a mountain range for instance), or if the 

 migration was too slow to escape the change. We have not the 

 space, nor at the moment any good reason, to explore this subject. 

 If interest warrants, a modern text on botanical evolution may be 

 consulted. 



What is more important today than extinction is the fluctuation 

 of quantity and quality in a valuable and useful species according 

 to the way man manages or mis-manages the environment. It is 

 quite true, however, that valuable species may for all practical pur- 



