14 . EDITOR'S PREFACE, 



it fiofured. The value of this new material will be appreciated when it is 

 known that it added 110 species to the already rich flora of the Dakota 

 Group. This bi'ings the total number of known species from the Dakota 

 Group up to 460. 



The task of the editor of a posthumous work is always a delicate one, 

 especially when any portion of such a work is left unfinished, for he is in 

 constant fear that he may not correctly interpret and carry out the wishes 

 of the author. I have, therefore, made hardly any changes, except those 

 expressly implied or called for in the notes left by Prof. Lesquereux him- 

 self As he worked upon this later, and in some respects richer material, 

 certain previous conclusions of his underwent modification ; thus, additional 

 material led him to change what had first been described as PhylUtes Masoni 

 to Ilex Masoni, Phi/llites cretaceus to Plataniis cretacea, etc. Changes of 

 this kind were not actually made by himself, 1)ut Avere indicated by notes. 

 Additional points of comparison among the s}>ecies were also suggested as 

 his work went on, and whenever indicated they have been carefully 

 attended to. 



The only specimens that had not been figured at the time of Lesque- 

 reux's death Avere purchased of Mr. Sternberg, together with many others, 

 by Mr. R. D. Lacoe, of Pittston, Pennsylvania. These Mr. Lacoe has cour- 

 teously placed at our disposal, nnd they have been drawn by Mr. F. Von 

 Dachenhausen, tlie artist (if tlie Paleobotanical Division. They number 30 

 figures, and fill Plates LXIV, LXV, LXVI. 



In a few instances the sjjecific names given by Prof Lesquereux to 

 new species were preoccupied; for example, '■'■ Celastrophyllum obovatum, sp. 

 no v.," is antedated by C. obovatum, of Fontaine ; ^' Mifiira pro-vhua, sp. nov.," 

 by the M. x>roxnrun\i Ettiugshausen, etc. Such names I have changed, and 

 liave indicated tlu^ fact in foot-notes. 



I have also changed the arrangement of some of the orders and genera 

 to make it conform to that in Bentham and Hooker's Genera Plantarum, or 

 rather have arranged them in the reverse order of this, since they proceed 

 from the lower to the higher plants. 



In conclusion, I beg to acknoAvledge my great obligation to Prof 

 Lester F. Ward, for counsel and valuable assistance ; to Mr. C. D. White, 

 who has verified all of the references ; to Prof. F. H. Snow, of the Univer- 

 sity of Kansas, who has supplied information that was lacking, and a 

 valuable series of specimens; and esjjecially to Mr. R. D. Lacoe, of Pittston, 

 Pennsylvania, who has generously placed Ins extensive and highly valuable 



