Xerophyte

Central Spines

1 to 4, somewhat thicker and longer, the same color as the radial, erected or outward-pointing, 3-4(-5) cm long, straight or very slightly curved.

Seeds

Microsemineum type, 0.5 × 1 mm; testa black, finely warty; hilum elongate oblique.

Description

Gymnocalycium monvilleiSN|11445]]SN|11438]] subs. horridispinum, best known in cultivation as G. horridispinum, is a very distinctive (usually) solitary geophytic cactus. It is recognisable at a glance, due to its strong, outstanding spine formation, and is among the few gymnocalycium species which can be fairly reliably identified from their general appearance, without recourse to flower-dissection seed studies or other methods. The spines are metallic grey with brownish tips, stout, strong and sharp. While most gymnocalycium species have flattened to almost spherical stems Gymnocalycium monvillei subs. horridispinum develops in age a somewhat columnar stem. The flower can be white with violet-pink edging to the petals, purple-pink or most often wholly pink. It is related to Gymnocalycium multiflorumSN|11438]]SN|11445]].

Flowers

Very showy, around the apex, funnel-shaped, they are some of the largest in this genus 6-7 cm long and wide, often growing larger than the plant, bright pink, occasionally, white with violet-pink edging to the petals or dark purple-pink. Pericarpel green with elongated red tipped scales scales gradually shifting to external tepals that are pink-purple with a greenish median strip. Internal tepals silky white or (usually) pinkish-lilac to pink with a pale pink throat. The flowers darken more or less after a day or two and take a purple tone. Filaments white; anthers bright yellow. Style white, stigma-lobes 8-10 lobes white.

Spines

Stout, strong, sharp and impressive, spreading to erect. Young spines blackish brown more reddish at the base with brown to gray tips. (Reddish brown wet). Later metallic grey with brownish tips.

Ribs

10-15 deep, acute, broad, with pronounced conical 'chins' below the areoles.

Stem

Usually solitary, globular to cylindrical (the plants tending to grow columnar even when young), upright, 8-18 cm in diameter, 15-40 cm high. Apex depressed, little or not woolly, but strongly spined. Epidermis shiny dark green, grey-green or olive green.

Radial Spines

9-12 (usually less in young plants) spreading, straight or slightly curved 2-3 (or more) cm long.

Fruits

Ovoid, 15 × 20 mm, dark green, slightly reddish when ripe.

Areoles

Ovate, 8-10 × 5-6 mm, yellowish white becoming pale grey in colour, with fine wool.