No. 16. Mammillaria johnstonii (Britton & Rose) Orcutt.
Neomammillaria johnstonii, Britton & Rose, The Cactaceae 4.80.1923
Mammillaria johnstonii, Orcutt, Cactography, 7, 1926.
Body:- Simple, occasionally caespitose from the base, globose with a slightly sunken apex, 15-20 cm. high.
The tubercles are arranged in 13 and 21 spirals, firm in texture, somewhat dull bluish-grey green, 4-angled the tip,
with milky sap, 10-13 mm. long, 6-9 mm. wide at the base.
The areoles are round to oval, with scant white wool but no bristles.
Spines:- Mostly two centrals, but occasionally 4-6 in the varieties, 10-25 mm. long, subulate, straight to occasionally tortuous,
smooth, stiff, light purplish to black, divergent, the upper one erect.
The radials are 10-18 in number and are 6-9 mm. long, the upper ones shorter, all acicular, stiff, straight, smooth, white to
cream with reddish-brown to black tips, slightly ascending,
Flowers:-Appearing near the top of the plant, but in old axils, campanulate, 15-20 mm. long and wide.
Outer perianth-segments reddish to purplish-brown tapering mid-stripe, bordered with pale green, pinkish-cream margins,
ovate-lanceolate, tip acute to obtuse, margins ciliate to serrate.
Inner perianth-segments pink to brownish mid-line to mid-stripe, white to cream margins,
linear-lanceolate, 1.5 to 2.5 mm. wide, tips acuminate, margins mostly entire with ends split.
Filaments pink, above, cream below
Anthers bright yellow. Style pale brownish-pink or sometimes greenish.
Stigma-lobes 6 or 7, olive-green, linear, 2 mm. long and just, overtopping the anthers.
Fruit:- Red to scarlet, clavate, 25 x 8mm., with dried perianth persisting.
Seeds:- Dull light,brown, curved pyriform with a lateral hilum, reticulate, 1.2 x 0.6 mm.
Distribution:- Sonora, Mexico.
Type Locality:-San Carlos Bay, near Guaymas, Mexico
From the Journal of the Mammillaria Society Vol. III n.3 June 1963
Mammillaria johnstonii SB 432
SB 432 - San Carlos Bay - Sonora - Mexico
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