This set combines both Gleason and Cronquist's Manual of Vascular Plants, Second Edition and its Illustrated Companion.
From the back of Manual of Vascular Plants of Northeastern United States and Adjacent Canada:
When Cronquist completely revised this second edition of the Manual, he rearranged taxa according to his phylogenetic system and the updated nomenclature. The general keys -- long known for their ease of use -- were revised, new synoptic keys added, and the glossary expanded. This second edition of the Manual relects an effort to incorporate into a single comprehensive account the results of modern taxonomic research on the flora of the area covered, with due regard to all past accounts, all in the light of Cronquist's critical evaluation. The aim is to make it possible for the user to come up with the correct name of a plant with only a hand lens, or sometimes a dissecting microscope, as accessory equipment.
From the back of Illustrated Companion to Gleason and Cronquist's Manual:
The book consists of 827 plates of meticulously rendered black-and-white botanical illustrations. Arranged and labeled to cross-reference with Gleason and Cronquist's Manual of Vascular Plants, Second Edition.