University of Pennsylvania, 



Philadelphia, April 1, 1878. 



Sir : I have the honor to transmit herewith my final report upon the 

 botanical collections made by the parties under your charge. 



In doing so, it is but fair to state how little of whatever merit the report 

 may have is due to myself, and how much to those who have assisted in 

 collecting the material, ami to those who subsequently aided in naming and 

 describing it. 



Dr. George Engelmann, of Saint Louis, has furnished reports upon the 

 numerous orders and genera that he is our acknowledged authority upon, 

 and these alone form no inconsiderable part of the whole. 



Professor Gray, of Cambridge, has throughout kindly settled all 

 doubtful points of nomenclature referred to him. Without his advice and 

 assistance, it would have been impossible for me to have completed the 

 work. 



The same may be said of the services of Mr. Sereno Watson. He has 

 also furnished the list and descriptions of the Leguminosse. 



Prof. Thomas C. Porter, of Easton, has worked up the Scrophulariaceae, 

 Polemoniacese, Labiatae, Borraginacese, and Polygonacese, orders which 

 together comprise a large part of the descriptive text. 



Mr. M. S. Bebb, of Fountain dale, 111., has written the account of the 

 Willows, which are confessedly among the most difficult of all American 

 genera. 



Dr. George Vasey, Botanist to the Department of Agriculture at 

 Washington, D. C, has made a careful report on the Grasses collected by 

 the Expedition; and Mr. William Boott, of Boston, Mass., contributes the 

 paper on Carex. 



XVII 



n BOT 



