Cheilanthes feei is a xerophytic fern that is broadly distributed throughout the United States west of the Mississippi. Although it has a broad distribution, it occupies a very narrow niche. In southeast Missouri, C. feei inhabits crevices of limestone bluffs, in full sun, approximately 0.5–1.0 m from the top of the bluffs. The physiological basis for the fern's restriction to this xeric environment is unclear. In this study, C. feei spores were subjected to a broad range of temperatures, pH, and light intensities, to varied light qualities, and to different moisture levels. Results indicate that C. feei spores can germinate under a wide variety of conditions. However, data suggest that spore germination optima and optimal conditions for protonemal growth overlap narrowly. The disparity in optimum conditions may be a partial basis for the broad distribution and narrow niche of C. feei.