Structure and identification

The stem is initially spherical, later club-shaped or cylindrical. In the monograph, it reaches up to 30 cm long and 9 cm in diameter. Tubercles have a flattened upper surface and a groove containing one or more red glands. The main central spine usually projects straight out, sometimes accompanied by shorter upper spines. Flowers of the nominate subspecies described are small and whitish yellow. The form historically treated as subsp. stipitata has a hooked central spine tip and almost white flowers. [Dicht and Lüthy 2005, p. 59–60]

Habitat and variation

The monograph associates the nominate subspecies with the lower slopes of limestone hills in central Mexico, often beneath shrubs. For the stipitata group, it also indicates volcanic hills and shelter from agaves and hechtias. Differences between these groups remain part of the species' variation. A young plant is much more slender and less heavily armed than an adult stem. [Dicht and Lüthy 2005, p. 59–60]

Stem tissues

The 2023 anatomical study covered three adult plants from each group described as C. clavata, C. cornifera and C. radians. In C. clavata, beneath the single-layered epidermis lay a hypodermis, a subsurface tissue comprising up to three layers of cells with unevenly thickened walls. It contained rounded and prismatic crystals. Mucilage cavities occurred in the stem cortex, which the authors did not find in the other two groups examined. Stomata were level with the epidermis. [Avila-Escobar et al. 2023, p. 234–235, 238–239]

In the wood, vessels were surrounded by wide-band tracheids, recognisable by ring-like or spiral wall thickenings. Vascular bundles also occurred in the cortical parenchyma. A 2016 comparison showed narrower vessel elements in tubercle bundles than in the central vascular cylinder in three adult C. clavata plants examined. The authors associated this arrangement with a possible restriction of flow to the tubercles. Cell structure was examined, without directly measuring water flow. [Avila-Escobar et al. 2023, 2023, p. 235–238; 2016, p. 2, 6–8 PDF, tab. 1–2] [Terrazas et al. 2016, 2023, p. 235–238; 2016, p. 2, 6–8 PDF, tab. 1–2]

Related articles

The Coryphantha tubercle. Development, identification and water conduction

Materials from the author's archive

The species also appears in Konrad Szychowski's private material archive. [Kaktusy i Inne 2005c, file p. 25]

Synonyms and names in the literature

Mammillaria clavata · Neolloydia clavata [2-WWW]