Geothallus

Geothallus is a monotypic genus of liverwort in the family Sphaerocarpaceae. Its sole species, Geothallus tuberosus, is a critically endangered species endemic to California in the United States. Described in 1896 by American botanist Douglas Houghton Campbell, it is commonly known as Campbell's liverwort.

Geothallus
Conservation status
Critically Endangered  (IUCN 3.1)[1]
Critically Imperiled  (NatureServe)[2]
Scientific classification
Kingdom:	Plantae
Division:	Marchantiophyta
Class:	Marchantiopsida
Order:	Sphaerocarpales
Family:	Sphaerocarpaceae
Genus:	Geothallus Campb.
Species:	G. tuberosus
Binomial name
Geothallus tuberosus Campb.
Synonyms[3]
Geocarpus tuberosus (Campb.) K.I.Goebel Sphaerocarpos tuberosus (Campb.) R.M.Schust.

Taxonomy and history

Geothallus tuberosus was described by American botanist Douglas Houghton Campbell in an 1896 article published in the Botanical Gazette.^[3][4] Campbell first noticed the new species in March 1895, having found an unfamiliar plant growing in a clump of Ophioglossum nudicaule he was cultivating. The O. nudicaule had been sent to him by a Katherine Brandegee, who collected them from sandy soil near San Diego, California. Mixed in with the O. nudicaule, the specimens were partially buried in the dirt and had lost much of their green colour due to desiccation. Campbell would only notice their uniqueness after rehydrating the clump of liverworts under a bell jar.^[5]

Distribution and habitat

Endemic to California in the United States, Geothallus tuberosus is known only from San Diego County and Riverside County. It can be found in small, isolated populations on mesas, coastal hills, and the Peninsular Ranges, where it grows in gravelly soil, at the edges of vernal pools, and on flat and gently sloping areas in and near chaparral.^[1][6]