This book provides keys, descriptions and illustrations for about 850 species of liverworts and hornworts, in 148 genera and 47 families, of Colombia and Ecuador. The largest genera are Lejeunea (66 spp.), Plagiochila (65), Frullania (54), Radula (33), Metzgeria (33), Cololejeunea (32), Cheilolejeunea (30), Bazzania (26), Drepanolejeunea (25), Ceratolejeunea (18), Diplasiolejeunea (18), and Syzygiella (18). Species descriptions include brief morphological characterization and discussion with emphasis on characters for identification, world range as well as distribution and habitat in Colombia and Ecuador. Classes, orders, families and genera are also described and the main features for recognition of the genera are briefly discussed. The introduction includes chapters on history of exploration, diversity and endemism, and classification. A glossary, bibliography and index to scientific names are alsoprovided.