EDITOR'S PREFACE. 



This volume upon the flora of the Dakota Group was the hist work 

 upon which Pruf. Lesquereux was engag-ed. He had ah-eady in his Creta- 

 ceous Flora^ and the Cretaceous and Tertiary Floras^ made extensive con- 

 tributions to the knowledge of Dakota Group plants, but by the discovery 

 of rich plant deposits in central and western Kansas, in Nebraska, Minne- 

 sota, and other places, much additional material was obtained. This ma- 

 terial had been collected from time to time until about 1885, when he set 

 to work to prepare a final monograph. The manuscript of this monograph, 

 which filled about 475 written pages and was accompanied by '45 quarto 

 plates, was completed and sent to the Director of the U. S. Geological Sur- 

 vey on February 21, 1888. It embraced descriptions and figures of 350 

 species of plants. 



A few months after it had been sent to Washington, and before it could 

 be taken up for publication, very extensive additional collections were made 

 in Ellsworth County, Kansas, by Mr. Charles H. Sternberg, and by the Mu- 

 seum of the University of Kansas, under the direction of Prof F. H. Snow. 

 This material, which numbered some thousands of specimens, was sent to 

 Prof Lesquereux for identification, and, although he was in feeble health at 

 the time and knew full well that his days for work must necessarily be num- 

 bered, he entered upon the tiisk with characteristic enthusiasm. He saw at 

 once that the material contained much that was new and interesting, and 

 in order that it might be incorporated in the monograph he asked that the 

 manuscript and plates be returned to him. This was done, and his last 

 days were spent in working ui) and adding this new matter, and at the time 

 of his death the material had all been identified and described and most of 



' Contributions of the Fossil Flora of the Western Territories. Part i : The Cretaceous Flora, 

 U. S. Geol. Survey of Terr., Vol. 6, Washington, 1874. 



^Contributions to the Fossil Flora of the Western Territories. Part III: The Cretaceous and 

 Tertiary Floras. U. S. Geol. Survey of Terr., Vol s, Wasljington, 1883. 



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