Homalocephala (plant)

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Homalocephala
Echinocactus polycephalus 4.jpg
Homalocephala polycephala
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Order: Caryophyllales
Family: Cactaceae
Subfamily: Cactoideae
Tribe: Cacteae
Genus: Homalocephala
Britton & Rose [1]
Type species
Homalocephala texensis
Species

See text.

Homalocephala is a genus of plants native to Mexico and the United States. [1]

Contents

Description

Plants in this genus differ from Echinocactus and Astrophytum by having stem that have few trichomes at the apex and acute ribs; flowers that are slightly tubular rather than campanulate; embryos that are campilotropous and acute cotyledons. [2]

Taxonomy

In the past, all three species have been considered to be in the genus Echinocactus . In 1922 by Nathaniel Lord Britton and Joseph Nelson Rose segregated E. texensis to its own genus Homalocephala based on differences in growth form and fruit morphology. Homalocephala was then moved to a subgenus of Echinocactus by Alwin Berger in 1929. The subgenus was elevated to a genus again in 2018 based on morphological and molecular evidence. [2]

Species

As of June 2025, Plants of the World Online accepts three species:

ImageScientific nameCommon nameDistribution
Echinocactus parryi.jpg Homalocephala parryi (Engelm.) Vargas & Bárcenas
syn. Echinocactus parryi		Devil's cushionMexico
Echinocactus polycephalus, Section 6 BLM 8197 RobbHannawacker.jpg Homalocephala polycephala (Engelm. & J.M.Bigelow) Vargas & Bárcenas
syn. Echinocactus polycephalus		Cotton top cactusS. California, S. Nevada, Arizona, Mexico
Homalocephala texensis.jpg Homalocephala texensis (Hopffer) Britton & Rose
syn. Echinocactus texensis		Horse crippler cactusSW. Oklahoma to NE. Mexico

References

  1. 1 2 "Homalocephala Britton & Rose | Plants of the World Online | Kew Science". Plants of the World Online. Retrieved 2025-06-07.
  2. 1 2 Vargas-Luna, Mario Daniel; Hernández-Ledesma, Patricia; Majure, Lucas Charles; Puente-Martínez, Raúl; Macías, Héctor Manuel Hernández; Luna, Rolando Tenoch Bárcenas (2018-11-13). "Splitting Echinocactus: morphological and molecular evidence support the recognition of Homalocephala as a distinct genus in the Cacteae". PhytoKeys (111): 31–59. Bibcode:2018PhytK.111...31V. doi: 10.3897/phytokeys.111.26856 . ISSN   1314-2003. PMC   6246732 . PMID   30483031.
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