The Ada Hayden Herbarium has the largest collection of Iowa plants and fungi, containing over 600,000 specimens of vascular plants, bryophytes, fungi, and lichens. Functioning primarily as a research facility important for taxonomic studies (occurrence, distribution, and relationships of plants), it is also used for identifying unknown plants. Specimens are loaned to specialists at other institutions around the world to support research. Loans from other institutions allow our researchers access to other herbaria. Recently, herbaria have become a source of materials to use in molecular studies and to support basic research on biodiversity.