Description of Turbinicarpus knuthianus

T. knuthianus [Click the image for more pictures]

Photo © Mark Faint

Bödeker, Monatsschrift der Deutschen Kakteen-Gesellschaft, 139-140, 1930

Body solitary or very often offsetting from the base and forming a group of plants. Individual heads spherical and up to 6 cm in diameter, shiny dark - leaf green. Apex somewhat sunken, more or less covered by the wool and spines from youngest areoles, however hardly completly enclosed. Ribs completely divided into tubercles, conical, about 9 mm long and at the base the same width, standing straight, blunt at the tip and in larger plants organized loosely in 13 and 21 spirals. Areoles in young plants bare, in older however and especially in the apex with white wool, which continues around the spine bundle with short, but robust wool. The real areole somewhat elliptical and hardly 1 to 2 mm large. Radial spines about 18-20, silvery white, 8 mm long, very thin needle-like, smooth, stiff, horizontally spreading, somewhat curved to the body and in the apical areoles often slightly yellowish, but without nodular thickening. Central spines only one, from the top of the areole, somewhat pointing out in front and curved above, to 10 mm long, slightly rougher than the radial spines, but of an equal colour and often (not always!) in the upper part hardly noticeably grey - to dark brown. Axil completely bare.

Flowers very numerous and willing from the wool covered apical areoles, even from still rather small plants and also appearing from the offsets, flat funnel-shaped, to 25 mm long and broad. Ovaries oval, 3 to 4 mm large, light green, bare and clearly separate from the short floral tube. Sepals oblong, slightly sharpened, sharp edged, carmine-brown with yellowish white edges, 6-8 mm long and 2 mm broad. Exterior petals of equal form, somewhat sharper, 2.5 to 12 mm large, bright pink-carmine coloured with broad, carmine-red back stripe. Internal petals slightly shorter, linear - lanceolate, but with more slender tips, bright purple-pink and often at the top slightly darker and somewhat slit. Filaments yellowish white, the outer delicate pink above, anthers yellow, style below pale-, above dark carmine-pink, the lobes rather wide, 5-6 small and whitish, outside furrowed pink and in the centre pink, radiating. Fruit oval, shiny green to brown. Seeds unknown.

Locality: Villar, San Luis Potosi, México.

Related taxa

T. knuthianus seems to be a transitional species between the lophophoroides aggregate of the "true" Turbinicarpus species, via T. laui, and the species of the saueri aggregate of the Gymnocactus species:

References

Monatsschrift der Deutschen Kakteen-Gesellschaft, 139-140, 1930

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