Astrophytum

Not to be confused with Astrophyton.

Astrophytum is a genus of six species of cacti, native to North America.^[2]

Astrophytum
Astrophytum myriostigma
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Order:	Caryophyllales
Family:	Cactaceae
Subfamily:	Cactoideae
Tribe:	Cacteae
Genus:	Astrophytum Lem.[1]
Type species
Astrophytum myriostigma
Species
A. asterias A. capricorne A. caput-medusae A. coahuilense A. myriostigma A. ornatum[2]

These species are sometimes referred to as living rocks, though the term is also used for other genera, particularly Lithops (Aizoaceae). The generic name is derived from the Greek words άστρον (astron), meaning "star," and φυτόν (phyton), meaning "plant."

Description

The species of the genus Astrophytum usually grow individually with spherical to columnar green shoots and reach heights of up to 1.5 meters. The shoots are often densely covered with fine white tufts of hair, but sometimes they are completely bald. There are 4–10 (rarely 3) very noticeable ribs that are not divided into cusps. The large areoles stand close together, but do not merge. The spike is variable. Spines may be present or may be missing entirely.

The funnel-shaped, large flowers are yellow or yellow with a red throat. They appear at the top of the shoots and open during the day. The pericarpel is covered with pointed scales. The cap-shaped seeds have a diameter of up to 2.5 millimeters with a brownish black seed coat which is almost smooth. The edge is rolled towards the sunken hilum.^{[citation needed]}

Species

Image	Scientific name	Common Name	Distribution
	Astrophytum asterias (Zucc.) Lem.	Sand dollar cactus, sea urchin cactus, star peyote	small parts of Texas in the United States and Mexico.
	Astrophytum capricorne (A.Dietr.) Britton & Rose	Goat's horn cactus	Coahuila regions of Northern Mexico.
	Astrophytum caput-medusae D.R.Hunt		Nuevo León, Mexico
	Astrophytum coahuilense (H.Moeller) Kanfer		Coahuila and Durango, Mexico
	Astrophytum myriostigma Lem.	Bishop's cap cactus, bishop's hat, bishop's mitre cactus	northeastern and central Mexico.
	Astrophytum ornatum (DC.) Britton & Rose – Monk's hood[2]	bishop's cap or monk's hood cactus	Central Plateau of Mexico.

Seedlings of Astrophytum spp.

A ripe fruit of A. caput-medusae with seeds and testa showing

Synonymy

The genus has several synonyms:

• Astrophyton Lawr., orth. var.
• Digitostigma Velazco & Nevárez
• Maierocactus E.C.Rost^[1]

There are a number of species synonyms sometimes seen:

Name	Synonym of
Astrophytum columnare	Astrophytum myriostigma
Astrophytum crassispinoides	Astrophytum capricorne var. crassispinoides
Astrophytum glabrescens	Astrophytum ornatum
Astrophytum niveum	Astrophytum capricorne var. niveum
Astrophytum nuda	Astrophytum myriostigma var. nudum
Astrophytum prismaticum	Astrophytum myriostigma
Astrophytum senile	Astrophytum capricorne
Astrophytum tulense	Astrophytum myriostigma