I'm on vacation, so only a short written accompaniment today. – Daniel

Lip fern, or lace-lip fern, is native to western North America, from British Columbia south to California and east to Montana. Given the diversity of environments within that large area, it is not surprising that it isn't found everywhere within the region. Using Cheilanthes gracillima as an example, here's a small survey of how different databases present the distribution information.

The USDA's PLANTS database operates on a state-by-state presence/absence mapping system, like so: Cheilanthes gracillima. While useful in a broad context, it isn't very precise; if you make the assumption that you might find the plant in eastern Montana or south of the California border, you will be searching for a very long time.

The Flora of North America improves upon the PLANTS map by delineating the extent of the distribution: Cheilanthes gracillima. If you are familiar with regional geography, these types of maps can often give some hint as to what limits the distribution of a species. For this fern, it seems it grows in hilly or mountainous areas that are not subject to extreme heat or cold.

That presumption seems to be borne out by examining both the county-by-county distribution map in Washington state and the Jepson Manual's distribution map in Californian Floristic Provinces. These distribution maps allow better inference about the habitat and ecological requirements of the species, particularly the Californian map as it uses ecological similarities for map subdivisions.

A different approach is taken by the British Columbia E-Flora Atlas Page for Cheilanthes gracillima, which uses point data to map the location of documented collections of the plant (i.e., herbarium specimens). Interestingly, you can add to the map the “BEC Zones” (or Biogeoclimatic Ecosystem Classification) layer (similar, though not equivalent to the California Floristic Provinces) and discover that lace-lip fern is found in a half-dozen or so different ecological regions in British Columbia, but only one or a few known records of Cheilanthes gracillima exist for each region. In all of the other distribution mapping schemes, the notion that this species is relatively uncommon is masked by the presentation of the data.