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INTRODUCTION TO PLANT GEOCxRAPHY 



[chap. 



their allies) are described in Chapter II and illustrated in Fig. 16. 

 They, too, have a long fossil history, both as the small herbaceous 

 types which we know today and as huge trees that flourished chiefly 

 in the Carboniferous period, when they evidently composed a large 

 part of the vegetation, at least in coal-forming swamps. Subse- 

 quently, near the beginning of the Mesozoic era, the tree types 

 appear to have become extinct, much as in the case of the giant 



Fig. 31. — Fossil Equisetineae. A, a Calamite, Calamites suckoxvi (x about i); 

 B, a Sphenophyll, Sphenop/iylltwi etnarginotuin ( :< about i). (Both after Zeiller.) 



