2 UNITED STATES GEOLOGICAL SURVEY— TERTIARY FLORA. 



tlcnce afforded on tlie relation of the groups of the formations, they expose, 



as in a written book, documents illustrative of the origin and the successive 



development of some of the predominant and more interesting types of the 



present vegetation of this country. 



Allow me here to give expression of my gratitude for the assistance 



which you have given to my work and the constant interest by which you 



have greatly encouraged it. 



Very truly and respectfully, yours, 



L. LESQUEREUX. 

 Dr. F. V. Hayden, 



United States Geologist, Washington, D. C. 



