THE PROBLEM OF DEVELOPMENT 247 



existing times, have made marked progress and become 

 dominant. 



Our rapid review of the plant groups of the past, made 

 possible by the magnificent work of specialists in fossil 

 botany, certainly impresses upon us the truth of the 

 poet's dictum: " The old order changeth, and yieldeth 

 place to new. ' ' It also throws some light on the problem 

 of development — perhaps sufficient to make us intellec- 

 tually humble. We have yet much to learn from the 

 fossil record, and probably there is much that we wish 

 to know that we shall never know. Yet we must needs 

 marvel that so many plant-traces have survived the 

 chances' and changes of countless ages. There is in life 

 " a strange coming and going of feet." The principle 

 involved in this statement is fully illustrated in human 

 history and in Nature. " Kingdoms come and go, Em- 

 pires rise and wane." It may not be inapt to apply the 

 term " imperial " to some of the Palaeozoic plant groups, 

 yet three of these are extinct, and two — the Lycopods 

 and Horsetails — are no longer imperial. Concerning all 

 these, one may exclaim: " How are the mighty fallen !" 

 Nature, pressing on to high fitness and perfect adjust- 

 ment, evidently " scraps " archaic machinery, and meets 

 changed conditions with changed or specially adapted 

 life-forms. Researches into the history of the plants of 

 the past, as well as knowledge of the lack of finality and 

 absolute fixity of present plant forms, suggest that as 

 there has been change in the past, so there may be 

 change in the future. Nature has not exhausted her 

 resources in the development even of the highest Angio- 

 sperm. Given external conditions to act as stimuli, we 



