From the preface:
"Sphagnum, widely known as peat moss, has a wide use in agriculture, horticulture, and floriculture. Living plants are colourful and add much to the beauty of wetlands. It takes little training to recognize the genus, and most of the sections are almost as easy to recognize. Yet they are scarcely noticed by field botanists, and even bryologists tend to avoid them; they have a reputation of being taxonomically difficult but this applies only to a subset of the species.
There are few taxonomic treatments of Sphagnum in North America, yet it is a fascinating genus whose species comprise an integral part of nearly all fresh-water wetlands. Almost all significant critical taxonomic characters are microscopic and require tedious dissections and staining, which, with a little practice can be easily self-taught. Even with a moderate amount of field experience, however, a novice can learn to recognize sections and some species in the field with certainty (although there are many species that even experts cannot distinguish without a compound microscope). All field identifications need to be confirmed microscopically. It is our hope that this treatise will aid those who venture into naming peat mosses."