Stenostephanus atrocalyx J.R.I.Wood

This species is accepted, and its native range is Central & S. Peru.


Wood, J.R.I. Stenostephanus (Acanthaceae) in Peru. Kew Bulletin 74: 64 doi:10.1007/s12225-019-9843-0

With an area of occupancy of 60,000 km2 and an extent of occurrence of 43768.144 km2, based on Geocat, this species should be provisionally classified as Endangered (EN) in its area of occupancy but only Near Threatened (NT) in its extent of occurrence according to IUCN guidelines. As the habitat is vulnerable to forest clearance and the populations are disjunct, all apparently lying outside protected areas, a provisional classification of Endangered (EN) would seem appropriate until populations and their habitat can be properly assessed.
Endemic to the Andes in Peru occurring in two slightly disjunct areas, one in southern Peru and the other in the central region.
Moist primary and secondary hill forest, often near streams, mostly between 1000 and 1500 m.
Morphology General Habit
Shrub 1 – 2.5 high
Morphology Leaves
Leaves slightly unequal in each pair, petiolate; lamina narrowly to broadly oblong-elliptic, 4 – 23 × 1.2 – 8.5 cm, acuminate, base attenuate and briefly decurrent, margin obscurely crenate, glabrous, adaxially with cystoliths, abaxially paler, veins c. 10 pairs, reticulate, with prominent cystoliths; petioles 0.3 – 2 cm
Morphology Reproductive morphology Flowers Androecium Stamens
Stamens exserted 1 cm, filaments glabrous, anthers 3 mm
Morphology Reproductive morphology Flowers Calyx
Calyx dark green to purplish, drying blackish, prominently parallel-veined, deeply 5-lobed to c. 1 mm above base, lobes linear-oblong, abruptly narrowed to a tiny point or mucro, the tips often spreading at anthesis, c. 6 × 0.5 mm but accrescent in fruit to 9 – 10 × 1 mm and becoming slightly oblanceolate, glabrous
Morphology Reproductive morphology Flowers Corolla
Corolla purplish-red or crimson, straight, glabrous, except for a few large-celled, spreading hairs at the apex, 1.7 – 2 cm long, tube constricted just above base, narrowly cylindrical for c. 4 mm then abruptly ventricose to 5 mm, becoming narrower towards the apex, obscurely 2-lipped, upper lip 3 – 4 mm, entire, lower lip slightly shorter, 3-toothed, the teeth c. 1.5 mm
Morphology Reproductive morphology Flowers Gynoecium Style
Style exserted, glabrous, stigma ellipsoid
Morphology Reproductive morphology Flowers Pedicels and Peduncles
Peduncles 11 – 21 mm, primary bracteoles linear-lanceolate 3 mm, secondary peduncles 4 – 8 mm, secondary bracteoles 1.5 – 2 mm, filiform; pedicels 2 – 5 mm
Morphology Reproductive morphology Fruits
Capsule 13 – 14 × 3 mm, clavate, glabrous, 4-seeded
Morphology Reproductive morphology Inflorescences
Inflorescence a solitary terminal narrowly pyramidal, lax thyrse, c. 7 – 24 × 4 – 5 cm (occasionally also with two axillary spikes arising from the axils of the basal bracts), rhachis glabrous, the dichasia in opposite pairs, the lowermost up to 3 cm apart, bracts at base of thyrse resembling reduced sessile leaves
Morphology Reproductive morphology Seeds
Seeds 2 × 1.5 mm, pale cream, reticulate, minutely puberulent.
Morphology Stem
Stems glabrous, weakly quadrangular
Distinguished by the inflorescence of lax thyrses, glabrous corolla and especially by the dark green (drying blackish) calyx with broad, linear-oblong lobes, abruptly narrowed at the apex and terminating in a fine mucro. No obvious close relatives have been noted apart from Stenostephanus wasshausenii described later in this paper, which has much larger floral dimensions. S. atrocalyx has been compared in collector’s notes with S. crenulatus but the calyx is much larger and different in shape. This species is named “atrocalyx” because of the dark colour of the sepals, which appear black in dried specimens. The leaves of this species are quite variable in shape, from oblong to elliptic. Collectors have noted that it is visited by hummingbirds, something that it is probably the case with other tubular red-flowered species such as Stenostephanus jamesonii and S. cuscoensis.
Peru, Cusco, Quispicanchis, along trail 25 km SW of Quincemil, 1340 m, 8 Oct. 1976, D. C. Wasshausen & F. Encarnación 744 (holotype US2957324, isotype K).

Native to:


Stenostephanus atrocalyx J.R.I.Wood appears in other Kew resources:

First published in Kew Bull. 74(4)-64: 6 (2019)

Accepted by

  • Govaerts, R., Nic Lughadha, E., Black, N., Turner, R. & Paton, A. (2021). The World Checklist of Vascular Plants, a continuously updated resource for exploring global plant diversity. Scientific Data 8: 215.


Kew Bulletin

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