42 FOSSIL FLORA OF THE SIERRA NEVADA. 



explorations of the Western Territories for the Department of the Inte- 

 rior, I have prepared each year for the annual reports of Dr. F. V. 

 Hayden, the director of the explorations, a review of the progress of 

 the discoveries in vegetable palaeontology, and given preliminary descrip- 

 tions of the species (1870-1875). And then a revision of all the 

 materials has been made for the preparation of the seventh volume of 

 the monographs of the survey, the "Fossil Flora of the Tertiary Forma- 

 tions of the Western Territories," which is now published. It describes 

 three hundred and thirty vegetable forms, represented in sixty-five plates 

 of illustrations. If to this be added the species described by Professors 

 Heer and Newberry, and those from Oregon, already described and fig- 

 ured, the number of North American Tertiary plants known up to this 

 time is not far from five hundred. With the Cretaceous species, they 

 constitute already an important amount of palaeontological data, which 

 may be used with advantage in botanical pursuits. 



Of course I have profited by these documents as far as it was possible 

 in preparing the present Report, which, however, may be received by 

 practical botanists with some misgiving; for the determinations of fossil 

 vegetable remains are extremely difficult, and generally somewhat uncer- 

 tain; and therefore the conclusions derived from their characters are gen- 

 erally considered as more or less unsatisfactory. In this case, however, 

 as the essential types of the plants of the auriferous gravel are very 

 distinct, and clearly represented by specimens in a good state of preser- 

 vation, I believe that they will be easily recognized even by botanists 

 unacquainted with palaeontology. 



In the table on pages 56, 57, will be found a synopsis of the essen- 

 tial points to be considered in regard to the deductions and conclu- 

 sions derivable from the relations of characters and of distribution of 

 species. 



I have to explain, first, why the number of the so-called new species 

 is so large for a list of a mere group of fifty plants. 



Until now the Pliocene floras of Europe have been scarcely considered, 

 though evidently they only can afford a key to the secret history of the 

 distribution of the present vegetation, in some countries at least, by 

 exposing the prefigurement of its characters. On this subject there is, 

 to this time, no work of importance, except the " Flora of Maxiinieux," 

 by Saporta and Marion. It is a splendid, remarkable work, indeed, which 



