Two species and changing genus boundaries
Plants of the World Online accepts Glandulicactus mathssonii and G. uncinatus. In the literature, both species also appear under names associated with Ferocactus, Ancistrocactus and Sclerocactus. Their transfer between genera reflects changing classifications in this part of Cacteae. The full epithet, name author and origin of the specimen studied are useful when comparing descriptions. [2-WWW]
In the 2019 regional flora, G. mathssonii was described as Ferocactus mathssonii. Britton and Rose's still earlier monograph separated Ferocactus crassihamatus and F. uncinatus. The first name corresponds to present-day G. mathssonii and the second to G. uncinatus. Anatomical and field data from these works retain their value when assigned to the current accounts. [Arias and Aquino 2019] [Britton and Rose 1922] [2-WWW]
A groove joining the areole to the tubercle base
The ribs are divided into distinct swellings. On the side facing the stem tip, a groove joins the spine-bearing part of the areole to the area near the tubercle base. In G. mathssonii, the current regional description indicates extrafloral nectaries in this area. Long spines, their hooked tips and the position of the groove together provide a set of useful identification features. [Arias and Aquino 2019, p. 98–102]
Britton and Rose described yellowish glands and nectar-like drops in G. uncinatus (called F. uncinatus in the monograph), near which bees were observed. This historical account documents insect visits. A protective function of ants has been demonstrated experimentally in some ferocacti, while for the cited Glandulicactus plants such a result remains a separate research question. [Britton and Rose 1922, Britton and Rose, p. 146] [Ness 2006, Britton and Rose, p. 146]
Spines and flower colour
Spine arrangement varies between specimens and as an areole ages. Strongly curved spines occur alongside straight ones, and one central spine may project well beyond the others. Flowers are shades of brown and reddish colours. The description of G. mathssonii from Guanajuato also gives pale margins on the inner tepals, yellow stigmas and red fruits opening at the base. [Arias and Aquino 2019] [Britton and Rose 1922]
Exceptionally long spines of G. uncinatus were documented in the Franklin Mountains of Texas. Their length was estimated from photographs containing an object of known size. The 2021 report describes local variation and individuals distinguished by the size of their spines. Details of the method and its scope are presented in the species account. [Gorelick 2021]
Range and species accounts
The natural range of G. mathssonii includes Guanajuato and San Luis Potosí. G. uncinatus occurs from southern New Mexico and western and southern Texas into Mexico. Data on site elevations and flowering dates concern specific parts of this area. They are developed separately in the accounts of the two species. [2-WWW]