REVIEWS 



The Laramie Flora of the Denver Basin. By F. H. Knowlton. 

 United States Geological Survey, Washington, Professional 

 Paper 130, 1922. Pp. 175, pis. 27. 



The Introduction deals with a history of Knowlton's investigations 

 of the Laramie flora, which were begun in 1889. His original intention 

 was to study the flora of the Laramie formation of the entire Rocky 

 Mountains. The older collections, which had served as a basis for the 

 work of Lesquereux, Newberry, and others, were to be critically reviewed, 

 and the new material was to be added, but the unsettled condition of 

 opinion regarding the Laramie group delayed the carrying out of this 

 plan, and it was finally decided to restrict the study to an area about 

 which there is little or no disagreement. Such is the Denver Basin in 

 Colorado. 



The paper deals with the plants known from the Laramie of the 

 Denver Basin, the material being derived from many sources. While 

 very considerable collections were brought together, Knowlton states 

 that the flora is neither large nor very impressive, because the fossil 

 plants of the Laramie are rarely found in great abundance. The matrix 

 in which Laramie plants occur is usually a soft, friable sandstone which 

 is not fitted to retain plant impressions with fidelity, and it is difficult 

 to find perfect specimens. In attempting to present as complete a 

 picture as possible of the plant life of the time, it has frequently been 

 necessary to describe forms on rather slender data. But they are all 

 figiured and described adequately enough to be recognizable in the 

 future. 



Part I gives a historical review of the Laramie problem; Part II 

 discusses the geologic relations and flora of the Laramie of the Denver 

 Basin; and Part III deals with the Laramie flora itself. A complete 

 hst of the Laramie plants in the Denver Basin is given, together with 

 various synonyms and changes of interpretation. The following genera 

 are predominant in the flora: 



Pteris Magnolia 



Sequoia Laurus 



Cycadeoidea Cinnamomum 



Juglans Platanus 



433 



