250 ESSAYS. 
tudes ; during which, having plentiful leisure, I tried my ’pren- 
tice hand upon some of the earlier natural orders. Before 
the expedition, as modified, was ready to sail, under the com- 
mand of Captain Wilkes, I had accepted Dr. Torrey’s propo- 
sal that I should be his associate in the work upon which I 
had made a small beginning as a volunteer. Two parts, or 
half, of the first volume (860 pages), of this Flora, were 
printed and issued in July and October, 1838. 
It was thought at first, in all simplicity, that the whole task 
could be done at something like this rate. But, apart from 
other considerations, it soon became clear that there had been 
no proper identification of the foundation-species of the earlier 
botanists, from Linnzus downward; and that our Flora could 
not go on satisfactorily without this. Dr. Torrey had, indeed, 
some years before, made a hasty visit to Hooker at Glasgow, 
to London, and to Paris; but the taking of a few notes upon 
some particular plants in the herbaria of Hooker, Lambert, 
and Michaux, and the acquisition, from Hooker, of a good set 
of the Arctic plants of the British explorers, was about all 
that had been done. I proposed to attempt something more ; 
so, taking advantage of a favorable opportunity, I sailed for 
Liverpool in November, 1838, and devoted a good part of the 
ensuing year to the examination of the principal herbaria, 
which I need not here specify, in Scotland (where the impor- 
tant one of Sir William Hooker still remained), England, 
France, Switzerland, and Germany, namely those which con- 
tained the specimens upon which most of the then-published 
North American species had been directly or indirectly 
founded, especially those of Linneus and Gronovius, of 
Walter, of Aiton’s “ Hortus Kewensis,” Michaux, Wildenow, 
Pursh, and the later ones of De Candolle and Hooker. 
After my return the work made good progress ; the remain- 
ing half of the first volume was brought out in the spring of 
the year 1840, and by the spring of 1843 the five hundred 
pages of the second volume, mostly occupied by the vast order 
Composite, had been issued. But meanwhile I had in my 
turn to assume professorial duties and incident engagements, 
— with the result that, although the study of North Ameri- 
