Epithelantha bokei

Name and distribution

Epithelantha bokei is a separate species in POWO, occurring naturally from southwestern Texas to northeastern Mexico. The name was published in 1969 (in older treatments, E. micromeris var. bokei or subsp. bokei). [2-WWW]

Spine covering and flowers

The stem is usually solitary, rarely branched, and 2–5 cm in diameter. A dense covering of appressed spines forms its smooth, creamy-white surface. The flora description usually gives 50–90 spines per areole, with lower values around 40, in more than three overlapping rows. Flowers are 1–1.7 cm long and of similar width. The North American sites lie on rocky sedimentary hills in the Chihuahuan Desert, usually at about 700 m, locally up to 1400 m. [Parfitt and Zimmerman 2003, t. 4, p. 239–240, Epithelantha bokei]

At the natural sites covered by this flora, flowering occurs in May and June, and flowers open in mid-afternoon. The account states that cross-pollination is required for reproduction. Fruits ripen later, from summer to autumn. These are observations of North American material. [Parfitt and Zimmerman 2003, t. 4, p. 239–240, Epithelantha bokei]

Association with the substrate

In the 2021 spatial analysis, E. bokei sites were associated with calcaric regosols. This result comes from comparing site frequencies among mapped soil categories. The value 3.662 used in the results is a Pearson residual from a contingency table, showing an excess of observations over expectations in this soil category. [Aquino et al. 2021, pp. 4524–4525, Fig. 3]

Hipoteza paedomorfii

In 2026, Gorelick described young E. micromeris from Anthony Gap in Texas with a pale, smooth covering and a concave apex. Larger, flowering stems in the same population had a rougher, grey surface and a convex apex. The resemblance of young stems to E. bokei led the author to propose paedomorphosis, the retention in a mature plant of traits corresponding to an earlier developmental stage of its ancestor. [Gorelick 2026, pp. 1–4]

The proposal concerns the course of development. Resolving it requires a comparison of the ontogeny of both species and their relatedness. Observations of the described E. micromeris population remain relevant to identifying young specimens, while the current POWO classification retains E. bokei as a distinct species. [Gorelick 2026, Gorelick, pp. 1–4. POWO, as of 11 October 2026] [2-WWW]

Adult plants in the 2019 revision

In a sample of 20 adult plants from four sites, Epithelantha bokei had 60–80 spines per areole. Their surface bore small persistent projections associated with remnants of spine epidermal cells. Electron microscopy showed these elements much more clearly than an ordinary view of the whole stem. Spine density and the persistence of the projections formed the first branch of the key to ten species. [Aquino et al. 2019, p. 601, 605–606, 610, 612, 615; tabela 5, ryc. 5A–B]

The samples examined formed a distinct, strongly supported lineage in the tree based on four plastid markers. This result concerns adult plants under the identification used by the authors. The later resemblance of juvenile E. micromeris to E. bokei concerns spine development and needs to be considered alongside separate data on adult plants. [Aquino et al. 2019, Aquino et al., pp. 606–609. Gorelick 2026, pp. 1–7] [Gorelick 2026, Aquino et al., pp. 606–609. Gorelick 2026, pp. 1–7]

Related articles