Polypodium californicum is a species of fern known by the common name California polypody.
It is native to Baja California and California, where it grows along the coastline as well as in moist spots in coastal foothills and mountain ranges in the southern part of its distribution.
In San Bernardino County, one is most likely to encounter it while hiking in the mountains, where it can occasionally be seen growing between rocks or along the crease of a fissure in a rock formation, as if by magic, where there is no visible soil to support it. Actually, the poypodium callfornicum does root itself in soil, doing so in a way that cannot be easily discerned.
This little fern often disappears when it dries out around midsummer, only to reappear with the very first rains of autumn, manifesting quickly and beautifully, as if it had never disappeared.
The polypody needs shade and moisture to establish itself, but needs almost no soil.
This polypody anchors with a scaly rhizome. A rhizome is a modified subterranean plant stem that is usually found underground, often sending out roots and shoots from its nodes. Rhizomes are also called creeping rootstalks and rootstocks. Rhizomes develop from axillary buds and grow at a right angle to  the force of gravity. The rhizome also retains the ability to allow new shoots to grow upwards.
If a rhizome is separated into pieces, each piece may be able to give rise to a new plant. The plant uses the rhizome to store starches, proteins, and other nutrients. These nutrients become useful for the plant when new shoots must be formed or when the plant dies back for the winter. This is a process known as vegetative reproduction
The polypodium californicum produces oval to triangular leaves up to 28 inches in length and just under 8 inches  in width.
The light green fronds of this fern project from along the length of a rhizoid; they do not emerge in a single bunch.
It’s common on moist, rocky soils and crevices at altitudes below 4,000 feet.  One can see large drifts of it along banks under oaks.
Each leaf is made up of many dull-pointed lance-shaped segments which may be thin or firm or somewhat fleshy, and have lightly serrated edges. The underside of each leaf segment is lined with a double row of flattened or sunken sori, which contain the spores.