Accurate taxonomy is essential to preservation and management of native grasses. Four problems in fescue taxonomy were investigated: the identity of the native fescue that dominates western Oregon and Washington prairies, the relationship of native Festuca roemeri to closely related grasses, the status of F. howellii and F. washingtonica, and fescue identification. The cespitose fine-leaved fescue that dominates prairies in western Oregon and Washington had previously been identified as F. rubra. Two fescues were found to dominate these habitats, one introduced F. rubra var. commutata, and the other native F. roemeri. The two differed in isozymes and subtle morphological traits. Isozymes, flow cytometry of DNA, and leaf anatomy clarified relationships among F. idahoensis, F. roemeri. and the northwest California fescue that shares characters with both of them. Isozyme band patterns divided them into two groups; F. roemeri and a mixture of populations of F. idahoensis and the northwest California fescue. All three fescues were tetraploid. All three fescues were distinguished using leaf anatomy. Festuca roemeri and the northwest California fescue shared leaves elliptic to obovate in cross section and usually having three sclerenchyma bands, at margins and midrib; F. idahoensis had leaves round to hexagonal in cross section, with five or more sclerenchyma bands, Festuca idahoensis and the northwest California fescue had numerous long adaxial leaf hairs; F. roemeri had few and short adaxial hairs. Leaf shape was phenotypically plastic in F. roemeri and the northwest California fescue, but constant in F. idahoensis. Leaf sclerenchyma development was greater in the field than greenhouse for all three fescues. The northwest California fescue was recognized as F. roemeri var. klamathensis B. L. Wilson fined. Morphometric analysis of F. howellii and F. washingtonica revealed that the two are distinct taxa. Festuca washingtonica appeared to be a rare species endemic to lightly grazed and ungrazed areas of eastern Washington. The F. howellii holotype was conspecific with F. elmeri, not F. viridula as previously thought. Because F. howellii is an earlier synonym, F. elineri must now be called F. howellii. Identification keys were provided for identifying fertile or sterile fescues and ryegrasses of the Pacific coast states. / Graduation date: 1999