The American Eclectic Dispensatory, 1854.
.html version copyright © 2016–2016 Henriette Kress.
King wrote this and printed it under the name "The American Dispensatory", and got told off by Coxe (or was it Wood?), who had written a book by that name a few years earlier ... King had to retract his print run and reprint with a different name. This didn't make for very good relations with the regulars.
Online versions and editions
You'll find various good scans on archive.org: 1st edition, 1854 - 3rd edition, 1856 - 5th edition, 1859 - 10th edition, 1876 - 17th edition, 1895, by John King and John U. Lloyd.
And on this site: 18th edition, 1898, by J. U. Lloyd and Harvey Wickes Felter
Part I. The natural order of plants. I've omitted it from this online version, but you'll find it in the pdf if you wish to read it. It's just a long list of orders, families, genera etc. with their botanical characters