A small stem and short spines
Pelecyphora minima (Escobaria minima in the account) was described in the 2012 comparison with a stem about 25 mm tall and 6–17 mm wide. Tubercles were 5–6 mm long. Each areole bore 14–27 short, strong, white spines, usually 3.5–6 mm long. Flowers were reported as deep pink to purplish pink, and seeds were 0.8–1.0 mm long. [Řepka and Gebauer 2012, p. 142, tabela 3]
The plant used for the spine study had a documented origin in Marathon, Texas. Current POWO accepts the name P. minima and confirms the species' range in southwestern Texas. The literature also uses the earlier names Escobaria minima and Coryphantha minima. [2-WWW]
A spine under the microscope
The surface of the spines examined lacked epidermal hairs. A single-layered, sclerified epidermis surrounded sclerenchyma fibres with elliptical outlines in cross-section. Their thickened walls reduced the cell lumina to small spaces. Mean wall thickness was 3.6 µm in the epidermis and 3.3 µm in the core fibres. The values concern preparations hydrated for 24 hours in water with glycerol. [Řepka and Gebauer 2012, pp. 139, 141, 143–145, table 2, figs. 1D and 2D]
The sample's structure fitted the two-zone organisation shared by four of the former Escobaria units examined. P. abdita had a distinctly different four-zone cross-section. The comparison has diagnostic value for the set examined and complements traits visible in the areole. Variation in this anatomy between P. minima populations lies outside the study's scope. [Řepka and Gebauer 2012, p. 138, 143–145]
Synonyms and names in the literature
Coryphantha minima · Coryphantha nellieae · Escobaria minima · Escobaria nellieae · Mammillaria nellieae · Neobesseya minima [2-WWW]