VIU PEEFACE, 



Society, who by his kind attention greatly facihtated our 

 labor. 



We are under deep obligations to Mr. Bentham, for much 

 important information, for the privilege of consulting his rich 

 herbarium, for many rare American plants, and especially for a 

 very full set of the plants collected by the late Mr. Douglas in 

 Oregon and California, w^hich w^ere confided to him, as Secretary 

 of the London Horticultural Society, for distribution. 



To Dr. LiNDLEY we are indebted for the opportunity of con- 

 sulting his very large herbarium, for many authentic specimens, 

 and for valuable suggestions. 



To Dr. Arnott our thanks are due for much very important 

 information, many valuable contributions to our herbaria, and 

 for the privilege of consulting his own excellent herbarium. 



To Prof. Don, for very obliging assistance in the examination 

 of the Linnsean herbarium. 



To Mr. Lambert, for the facilities afforded us in examining 

 the plants of Pursh, Bradbury, Mr. Nuttall, &c. which form a 

 part of his very large collection. 



To Dr. BooTT, for kind assistance in the determination of 

 the species of several difficult genera. 



To Mr. Fraser, for the privilege of examining the herbarium 

 of Walter in his possession. 



To Prof. Adrien de Jussieu, for the opportunity of consulting 

 his own herbarium, and that of his distinguished father, which is 

 authentic for many species of Lamarck, Poiret, &c. : to his kind 

 offices also, as well as to Mr. Decaisne, Assistant Botanist in the 

 Museum of the Jardin des Plantes, we are indebted for many 

 facilities in consulting the vast collections of that establishment, 

 comprising the herbarium of Michaux, and many others of much 

 interest to the North American Botanist. 



To Baron Benjamin Delessert, for access to his immense 

 herbarium and very complete botanical library. 



To Mr. P. Barker-Webb, for obliging assistance in the exami- 

 nation of the North American plants of the herbarium of Des- 

 fontaines, and the other collections which are incorporated in his 

 vast herbarium. Also to Mr. Spach, of the Jardine des Plantes, 





