Xerophyte

Central Spines

1 neither stronger nor longer.

Seeds

0.9 mm wide and 1.1 mm long, cap-shaped. Testa glossy black.

Note

'occidentalis' for the occurrence in the far western part of the area of distribution (central Paraguay).

Flowers

Several at a time from the apex, lemon-yellow 40-60 mm long and 50-70 mm wide. Buds covered by dark brown wool. Pericarpel green wrapped with brown wool and long stinging bristles. Bracts on the tube 5-10 mm long with brown wool and 2-3 bristles in the axil. Tepals lanceolate, shiny, lemon-yellow, often reddish in the outside, about 6 mm wide and 25-36 mm long. Stamens yellow 9-13 mm long. Style grooved 20-22 mm long and 2 mm thick, the 7-8 purple stigma lobes are 3-4 mm long. The plant is self-fertile.

Ribs

Mostly 7, vertical, to 30 mm wide and 15 mm tall almost triangular in cross-section. The sharp rib edges are broken into humps and valleys (up to 2 mm deep).

Stem

Flattened spherical, 20-50 mm tall and 30-60 mm (sometimes up to 70 mm) in diameter, dark blue-green to olive green, sometimes violet brown in the sun.

Radial Spines

5, rarely 7, spreading, curved, 5-20 mm long brown, occasionally dark brownish-black and soft or lighter amber-brown.

Fruits

Barrel-shaped, 5 mm wide and 11 mm long, withering when ripe, splitting open along irregular fissures.

Areoles

Roundish, small, white woolly, slightly recessed and 8 -12 mm apart mostly 2 mm high and 5 mm wide.