Wolf lichen (Letharia vulpina (L.) Hue) Collected by Theodore L. Esslinger in Klickitat County, Washington, August 10, 1999, unknown maker from the United States

An herbarium is a systematically arranged collection of preserved plants. The R. L. McGregor Herbarium houses approximately 400,000 specimens collected over the past 150 years. These include dried plant specimens (exsiccatae), seeds, and boxed and fluid-preserved vascular plant specimens. The herbarium also houses the largest single collection of plants from the grassland biome of central North America, as well as the largest collections of lichens and vascular plants from Kansas.

This variety of lichen is found among living and dead conifers in parts of western and continental Europe, the Pacific Northwest, and the northern Rocky Mountains of North America. This species is somewhat toxic to mammals, and has been used historically as a poison for wolves and foxes and by many Native American peoples as a pigment source for dyes and paints.