Edward Tuckerman's book is a pioneering work in the field of lichenology, the study of lichens, the composite organisms that result from the symbiosis of fungi and algae. Through years of meticulous research and analysis of specimens collected throughout North America, Tuckerman provides a comprehensive and systematic classification of lichens, their structures, reproduction, and distribution. His work inaugurated a new era in the study of lichens and continues to be a valuable resource for botanists, ecologists, and naturalists. This work has been selected by scholars as being culturally important, and is part of the knowledge base of civilization as we know it. This work is in the "public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work. Scholars believe, and we concur, that this work is important enough to be preserved, reproduced, and made generally available to the public. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant.