10 FLORA OF LOWER COAL MEASURES OF MISSOURI. 



the lines of specific differentiation have been drawn more closely than they 

 have usually been drawn in American literature, for the reason that a 

 greater systematic refinement, if the types are uniform and are satisfacto- 

 rily differentiated by the descriptions and illustrations, will better serve the 

 purposes of stratigraphic paleontology. 



A small number of species recorded by Professor Lesquereux as occur- 

 ring in Henry County, Missouri, have not been found in the collections to 

 whicli I have had access. These will be sjDccially enumerated at the close 

 of this report, although there is evidence that the record of several of 

 them is based on geographic errors. Certain others will be met under 

 different and sometimes unfamiliar names. A number of nomenclatural 

 changes have been made in conformity with the rules generally observed 

 by American zoologists or botanists. 



The systematic arrangement, like that employed in previous publica- 

 tions, is in part temporary. Many questions of the classification of com- 

 mon Paleozoic species are still under debate, pending the acquisition of 

 farther knowledge of the internal structure, fructification, or geologic 

 history of the various types. In the synonymy the references are chiefly 

 confined to illustrated material. Effort has also been made to point out 

 other plants in America or Europe that are closely related to our species, 

 and to indicate the most important specific differences between them. 



