Rosa woodsii (Rosaceae) Wild rose (Photo by Tom Ranker) The Herbarium houses a diverse collection of approximately a half million specimens of vascular plants, bryophytes, and lichens. These collections represent the most complete documentation of the flora of Colorado in the world. Herbarium COLO also has strong holdings from the southern Rocky Mountain region. This regional strength is enhanced by collections from western North America, the American Arctic, the Altai and the Caucasus Mountains of Central Asia, the European alpine, and the Sierra Madre Occidental of Mexico. These latter collections provide important comparative material that assist students, researchers, and monographers in their eforts.