250 ESSA YS. 



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 (360 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 Linnaeus 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 Linnaeus 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- 



