Pelecyphora missouriensis

Two samples of the nominate subspecies

Řepka and Gebauer's study included two samples of Pelecyphora missouriensis. The plant from Electric in Park County, Montana, was identified as Escobaria missouriensis subsp. missouriensis, and the plant from Holbrook in Navajo County, Arizona, as subsp. navajoensis. The material was kept in cultivation, and its provenance was given in table 1. All anatomical observations concern these two samples. [Řepka and Gebauer 2012, p. 140–141, tabela 1]

In the currently accepted POWO classification, the former subsp. navajoensis is a synonym of P. missouriensis subsp. missouriensis. Both historical identifications thus fall within the nominate subspecies, although they retain separate measurement series in the study. Data from these samples were not applied to subsp. asperispina. [2-WWW]

Hairs and spine cell walls

In both samples, unicellular, unbranched hairs grew from the spine surface. They were shorter in the Montana material, and longer and often curved, with a more pointed tip, in the Arizona plant. These projections arose from cells of the sclerified epidermis. Both samples had a two-zone cross-section, with an epidermis surrounding a mass of thick-walled fibres with small lumina. [Řepka and Gebauer 2012, pp. 139, 143–145, figs. 1B–C and 2B–C]

Mean epidermal wall thickness was 4.5 µm in the Montana sample and 3.6 µm in the Arizona sample. Corresponding means for core fibres were 3.7 and 4.0 µm. Measurements were made on hydrated material, with 15 measurements of each trait. The authors considered the possibility that longer hairs increase stem shading, but their study primarily documented structure. Thermal function and consistency of the trait between populations would require separate measurements. [Řepka and Gebauer 2012, pp. 141, 144, Table 2]

Historically compared differences in habit

In the morphological table, material identified as subsp. missouriensis was described with stems 25–50 mm tall and 38–100 mm wide and 6–20 spines per areole, 10–20 mm long. The former subsp. navajoensis was reported to have smaller stems, 10–15 mm, exceptionally up to 30 mm tall, and 10–15 mm wide, with 6–8 spines 2–4 mm long. This historical contrast contributed to separating the material in the publication. Under the current broader circumscription of the subspecies, it shows the range of variation previously distinguished. [Řepka and Gebauer 2012, p. 142, tabela 3]

Materials from the author's archive

The species also appears in Konrad Szychowski's private material archive. [Kaktologia 2009b, file p. 9] [Neciu b.d., file p. 1] [Sukulenty b.d.b, file p. 2] [Bydgoski Klub Miłośników Kaktusów 2002, file p. 7]