\ HI 1NTUOIHTTOKY. 



Edward Tuckennan has determined the Lichenes. For the remaining 

 portions of the text I am responsible. 



The collections on which this catalogue is drawn up wen- furnished 

 almost entirely by the various collectors attached from time to time to the 

 Survey under your charge, Dr. Hoffman, Dr. Loew, Prof. John Wolf, 

 and myself obtaining the greater part. They have been obtained 

 from Utah, Nevada, Colorado, New Mexico, Arizona, and California. 

 There is thus brought together a large number of species, with their 

 descriptions, that have hitherto been so scattered through our botanical 

 literature as to be practically unavailable to a large portion of those who 

 are interested in the botany of the regions embraced by this report. 



I have the honor to be, very respectfully, your obedient servant, 



J. T. ROTHROCK. 



To First Lieut. Geo. M. Wheeler, 



Corps of Engineers, in charge of 



United States Geographical Survey. 



