A. californica often grows as colonies of flat rosettes of light green, rigid thalli, with undersides dark wine-red to nearly black.

[6] Antheridia are clearly circumscribed, slightly elevated, strongly papillate, oval to linear-oblong, sometimes forked discs, situated in the median line of the thallus at some distance back from the apex.

[5] While working on male individuals in his laboratory George Pierce observed, then measured, antherozoids–packets of ciliated sperm cells and encasing slime–being "forceably ejected" from the thallus.

[7] Each "umbrella", or archegoniophore, is clearly visible raised above the thallus of mature female plants is not itself a sporophyte but is in fact gametophyte tissue.

This moves the fertilized archegonia outward and the receptacle eventually folds over to orient the developing sporophytes so that they face down.

[10] The genus name Fimbriaria was used by Bolander in his catalogue of plants growing in the vicinity of San Francisco in 1870, but it is antedated by Asterella.

[3] The genus name means "little star" in reference to the star-like appearance of pores in the thallus of some species as viewed from above.