THE FLORA OF NORTH AMERICA. 249 
number of species, collected by Bradbury on the upper Mis- 
sourl, 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 Frasers 
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 Phen- 
ogamous and Filicoid plants, and 38076 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 such 
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, his 
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 “ Flora 
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- 
