THE HISTORY OF GYMNOSPERMS 



THE HISTORY OF GYMNOSPERMS 



By Professor JOHN M. COULTER 



UNIVERSITY OF CHICAGO 



"'VTO great group of plants seems to have left so continuous and full 

 -'-^ a record of itself, through so long a stretch of time, as have the 

 Gymnosperms. Further work may uncover equally extensive records of 

 certain other vascular groups, but our knowledge of the history of 

 Gymnosperms is at present more complete than that of any other group 

 of plants. 



Several things have contributed to the completeness of this knowl- 

 edge of Gymnosperms. They have always been abundant in the flora 

 of every period that has left a plant record, and they are still abundant. 

 This has given continuity and wealth of material throughout the whole 

 history of vegetation, so far as that history is known. Those who pic- 

 ture an historical succession of the great plant groups are not repre- 

 senting the records in sight, for our earliest records show a vegetation 

 as varied and complex as that of to-day, so far as the great groups are 

 concerned. Although Angiosperm.s are probably relatively modern, 

 seed-plants were represented early in the Paleozoic by Gymnosperms. 

 This means that the evolution of the plant kingdom, in all its essential 

 outlines, had been attained at least as early as any known records of 

 vegetation. 



Another fact which has contributed to the completeness of our 

 knowledge of the group is what may be called the renascence of paleo- 

 botany as a morphological subject. Not only did this involve the com- 

 parative stud}^ from sections, of the essential structures, but also it 

 enormously extended the range of structures used in indicating rela- 

 tionships, by including the vascular system in the evolutionary scheme. 

 The incorporation of vascular anatomy into modern morphology was 

 significant not merely because it supplied another line of attack, but 

 also because it deals with the most completely recorded structure of 

 vascular plants and really gives continuity to the paleobotanical record. 



The Gymnosperms were represented during the Paleozoic by two 

 great groups, Cycadofilicales and Cordaitales. They were not merely 

 members of the Paleozoic flora, but they were conspicuous members, to- 

 gether constituting the seed-plant vegetation. Neither of these groups 

 has been traced with certainty into the Mesozoic, so that even though a 

 few lingering forms may be found at a later period, they are essentially 

 restricted to the Paleozoic, and our knowledge of them has been derived 



