This 2001 book provides a selective annotated bibliography of the principal floras and related works of inventory for vascular plants. The second edition was completely updated and expanded to take into account the substantial literature of the late twentieth century, and features a more fully developed review of the history of floristic documentation. The works covered are principally specialist publications such as floras, checklists, distribution atlases, systematic iconographies and enumerations or catalogues, although a relatively few more popularly oriented books are also included. The Guide is organised in ten geographical divisions, with these successively divided into regions and units, each of which is prefaced with a historical review of floristic studies. In addition to the bibliography, the book includes general chapters on botanical bibliography, the history of floras, and general principles and current trends, plus an appendix on bibliographic searching, a lexicon of serial abbreviations, and author and geographical indexes.

Thomas C. Porter, along with John M. Coulter, prepared a synopsis of the plants of the Colorado Territory, based on collections made from 1861 until 1873.