PREFACE. IX 



for specimens of many North American plants cultivated in that 

 establishment. 



To Prof. De Canuolle of Geneva, for the important privilege 

 of freely consulting his large herbarium through all the families 

 which are now published in his Prodromus, and for duplicates 

 of many interesting plants of the Order Composita:. 



To Dr. E.vdlicheu, Curator, and Dr. Fenzl, Assistant Curator 

 of the Imperial herbarium at Vienna, for assistance in consulting 

 that rich collection. 



To Dr. VoN Martius of Munich, and to Prof. Zuccarini, for 

 access to the Royal Collections and Garden under their charge. 

 To Prof. Schlechtendal of Halle, for the privilege of consult- 

 ing his own herbarium, as well as that of Schkuhr, of which he 

 has charge, and for the communication of an interesting set of 

 Mexican plants. 



To Dr. Klotszcii, the Curator of the Royal herbarium at 

 Berlin, for the greatest attention in facilitating the examination 

 of the herbarium of Willdenow and the other rich collections of 

 that establishment ; and for his aid in procuring for us specimens 

 of American plants from the Botanic Garden. 



To Prof. KuNTH of Berlin, for the opportunity of consulting 

 his herbarium, with the view of comparing several IVorth Ameri- 

 can plants with species from Mexico and New Spain collected 

 by Baron Humboldt. 



To Dr. Trinius and M. Bongard, of the Imperial Acad- 

 emy of Sciences of St. Petersburg, for the communication of 

 many plants from Russian North America and the adjacent 

 Islands. 



To Prof. Lehmann of Hamburgh, for the privilege of examin- 

 ing the genera Potentilla, GEnothera, &c. in his herbarium, and 

 for many very interesting specimens in these and other genera t 

 also for a small collection of Greenland plants, made for the 

 most part by the younger Vahl. 



To Mr. Nuttall we are indebted for a nearly complete 

 suite of the plants collected during his recent journey across the 

 Rocky Mountains to Oregon and Califol-nia, accompanied with 

 manuscript descriptions of the new genera and species : also for 



B 



