Xerophyte

Habit

Gymnocalycium robustumSN|25919]]SN|25919]] is a slowly growing succulent species, usually solitary.

Central Spines

Absent.

Seeds

Round-truncated, symmetrical, 1,2 mm long and strong, black, with cuticle usually completely separate from the testa and it will then appear as brown, much wrinkled. Hilum-micropilar area oval, 0,9 mm long, 0,6 mm wide.

Description

Gymnocalycium robustumSN|25919]]SN|25919]], as the name states, is a robust, rugged cactus species characterized by thick ribs and round podaria (tubercles) with few short spines and thick receptacles and fruits. Previously, it was circulated under the name Gymnocalycium cordobensis.

Roots

It has a central, robust, obconical rootstock about 5 cm long and up to 2 cm in cross-section.

Flowers

2-3 at any one time near centre of plant, wide funnel-shaped, up to 6 cm (rarely to 7 cm) long and up to 6 cm broad, white with a pink throat. Receptacle funnel-shaped, up to 45 mm long, 8 to 14 mm in diameter, scales almost semicircular, wider than longer 4 mm long, 6 cm wide, succulent, grey or with a touch of red. Pericarpel more or less conical, up to 30 mm long, 5-8 mm in diameter. Ovary conical, up to 20 mm cm long, 5 mm in diameter. Pistil cylindrical, white with small bump, very short, up to 13 mm long, 2 mm in diameter. Stigma with 8-9 (- 14) lobes, bright yellow, up to 3 cm long. Nectar chamber pink, 4 mm long. Stamens, erect, parallel, filaments white, shorter than the stigma up to 11 mm long, anthers yellow 2 mm long and 1 mm wide. Inner perianth segments white, pink at the base, narrowly lanceolate, acute. Outer segments like the scales, but longer and translucent .

Spines

5-7 stiff, up to 15 mm long. One of them pointing downward, the other irregularly protruding sideways. In the dry state, the spines are white as chalk, if wetted they become yellowish with brown part at the base.

Ribs

9-11 straight very flat, blunt, 15 mm high, 20-35 mm wide divided into 3-5 low, rounded tubercles (up to 5 mm tall), with transverse furrow and with chin-like protrusions (podaria) beneath each areola.

Stem

Spherical or hemispherical depressed at apex, 3-5 cm tall and 8-11 cm in diameter grey or greyish-green with a touch of mauve.

Fruits

Club-shaped or rarely spindle-shaped grey, pruinose, 40-45 mm long and 15-18 mm in diameter.

Areoles

Elliptical, approx 6 x 3 mm wide, with white tomentum.