THE FLORA OF NORTH AMERICA. 249 



number of species, collected by Bradbury on the upper Mis- 

 souri, in what was then called Upper Louisiana, — much to 

 the discontent of Nuttall, who was in that region at the same 

 time, and who, indeed, partly and imperfectly anticipated 

 Pursh in certain cases, through the publication by the Prasers 

 of a catalogue of some of the plants collected by Nuttall. 



To come now to the extent of Pursh's Flora, published 

 nearly sixty-nine years ago. It contains 740 genera of Phaen- 

 ogamous and Filicoid plants, and 3076 species, — just about 

 double the number of species contained in Michaux's Flora 

 of eleven years before. 



I must omit all mention of more restricted works, even Bach 

 as Nuttall's " Genera of North American Plants," which came 

 only four years after Pursh's Flora; also the " Flora Boreali- 

 Americana" of Sir William Hooker, which began in 1829, 

 but was restricted to British America. I cannot say how early 

 it was that my revered master, Dr. Torrey, conceived the idea 

 of the Flora which he at length undertook. But he once told 

 me that he had invited Nuttall to join him in the production 

 of such a work, and that Nuttall declined. This must have 

 been as early as the year 1832, that is, half a century ago. 

 My correspondence with Dr. Torrey began in the summer of 

 1830, when I was a young medical student, and three or four 

 years afterward I joined him at New York and became, for 

 a short time, his assistant, for all the rest of his life, hifl 

 botanical colleague. He was very much occupied with his 

 duties as professor, chiefly of chemistry; he had not yet aban- 

 doned the idea of completing his " Flora of the Northern and 

 Middle States," the first volume of which was finished in 

 1824, while yet free from all professional cares. Although 

 working in the direction of the larger undertaking, the " Blora 

 of North America" did not assume definite shape before the 

 year 1835. I believe that some of the first actually-prepared 

 manuscript for it was written by myself in that or the follow- 

 ing year. I was then and for a long time expecting to accom- 

 pany the South Pacific Exploring Expedition, as originally 

 organized under the command of Commodore Ap Catesby 

 Jones, but which was subject to long delay and many vicissi- 



