Pterocactus araucanus

Growth form and stem surface

Segments have a tuberculate surface, and areoles lack dense woolly hairs. In the morphological comparison, central spines are cylindrical and about 3 mm long. Flowers form at the segment apex, while the lower part is connected with the perennial underground system. [Las Peñas and Bernardello 2021, Table 2]

The epidermis study showed curved papillae, small projections of individual cells. Their bases have distinct striations, while their tips are smooth. The ordinary cuticle between them has faint, irregular striations. The different scale of these traits distinguishes them from macroscopic tubercles of the whole segment. [Faigón et al. 2011]

Patagonian material and relationships

The 2021 analysis included specimens from Chubut, among others. The species was classified among representatives of southern Monte and Patagonian environments. In the chloroplast tree it grouped with P. hickenii, with the P. neuquensis lineage separating earlier. [Las Peñas and Bernardello 2021]

DNA content was used to estimate a level corresponding to 2n = 132, or twelve basic sets. In this paper it was not a direct chromosome count for P. araucanus. Distinguishing DNA quantity measurement from chromosome counting preserves the record's proper precision. [Las Peñas and Bernardello 2021, Table 1]

Pollen development

Microspore tetrads and bicellular pollen released at maturity were observed in the anthers. Its surface has pores distributed around the grain and small spines on the outer wall layer. The comparative study also included P. australis, P. hickenii and P. valentini. [Gotelli et al. 2009]