Aptosimum decumbens Schinz

Kolberg H., van Salgeren M. 2016. A synopsis of Aptosimum and Peliostomum (Scrophulariaceae) in Namibia, including the description of a new species, Aptosimum radiatum, and keys to all accepted species. Kew Bulletin 71:16. DOI 10.1007/S12225-016-9628-7

Type

Type: Namibia, Hereroland, Lüderitz 105 (lectotype Z-28248!, selected here) — see Notes.

Morphology General Habit

Shrub, decumbent to prostrate, 5 – 20 cm tall, diam to 200 cm, not spinescent

Morphology Stem

Stems much branched, decumbent to prostrate, terete, to 100 cm long, glabrescent at base to densely short glandular-pubescent at tips, with many leafy short axillary shoots

Morphology Leaves

Leaves alternate, densely arranged, covering internodes, often borne at right angles to ground, narrow-elliptical, lanceolate, oblong-lanceolate to oblanceolate, (12 –) 30 – 50 × 2.5 – 12 mm, glabrous to sparsely short glandular-pubescent above, more densely so beneath; apex obtuse or rounded, rarely acute, shortly apiculate; base sessile to subsessile, attenuate; midrib prominent beneath, not spinescent; margins scabrid

Morphology Reproductive morphology Flowers

Flowers mostly solitary in axils of foliose bracteoles, sometimes in pairs or in c. 7-flowered dichasia, sessile to shortly pedicellate; pedicel 1 – 2 mm long; bracteoles linear to lanceolate, apex acute, base cuneate, 5.5 – 10 mm long, pubescent with ciliate margins towards base

Morphology Reproductive morphology Flowers Calyx

Calyx lobed to near base; tube < 1 mm long; lobes linear-lanceolate to filiform, 5 – 10 × 0.5 – 1.25 mm, sparsely stipitate-glandular outside and inside, apex acute, margins with long, multicellular, erect glandular hairs

Morphology Reproductive morphology Flowers Corolla

Corolla 12 – 20 mm long, short-glandular pubescent outside; tube 12 – 14 mm long, narrow in basal 4 – 5 mm, widening to a diam of c. 5 mm at mouth, mouth oblique, cream to pale violet outside, white inside; lobes broadly obovate, subequal, 3 – 4 mm wide at base, to 6 mm wide at rounded apex, inside purple to deep blue, dark patches at base

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens four, unequal, filaments with membranous margins, longer pair 6 – 8 mm long, shorter pair c. 3.5 mm long; anthers of longer stamens 3 – 4 mm long, those of shorter pair c. 2 mm long, ciliate-hispid, with tuft of hairs at apex

Morphology Reproductive morphology Flowers Gynoecium Ovary

Ovary obovoid, compressed, short-pubescent; nectary cup-like, 0.75 – 1 mm high; style filiform, thicker towards tip, c. 20 mm long, sparsely short hairy at base; stigma somewhat emarginate

Morphology Reproductive morphology Fruits

Capsule broadly obovoid, 4 – 6 × 5 – 7 mm, densely short-pubescent, reticulate; apex somewhat compressed and weakly emarginate, margins of valves densely papillose

Morphology Reproductive morphology Seeds

Seeds brownish-black, tuberculate; funicle lunate, thickened

Distribution

Africa: Angola, Botswana, Namibia, South Africa.

Ecology

Found predominantly in sandy soil on calcrete plains or gentle slopes, dolomite formations and interdunal streets. Recorded in the woodland, shrubland, savanna, Kalahari sands, floodplains, drainage areas and river valleys, Karstveld and thornbush shrubland vegetation types (Mendelsohn et al. 2010). Present in the Zambesian Domain and Highlands to 1500 m phytogeographical groups (Craven 2009). Altitude: 915 – 1630 m.

Conservation

This species is widespread and occurs in large populations so that the EOO and AOO are above the threshold for threatened categories according to criterion B (IUCN 2012, 2013). No threats could be identified and it is therefore evaluated as LC here.

Phenology

Flowering and fruiting throughout the year. Peak flowering: Jan. – April. Peak fruiting: Jan. – May.

Vernacular

edinbulufi, odimbulufi, ektadiai (Oshikwanyama, Namibia); ndungati (Rukwangali, Namibia).

Note

Lüderitz 105 at Z is selected here as the lectotype over Schinz 513 at Z and ZT because of the better quality material. Schinz (1890: 184) cited specimens by Lüderitz and Schinz without collector's numbers, only localities. Specimens at Z and ZT with these localities, however, have the collector's numbers 105 and 513 respectively and are annotated as Typus. Aptosimum decumbens is closely related to A. patulum Bremek., A. gossweileri Skan, A. molle Skan, and A. schinzii Emil Weber; the type specimens of these species all look very similar. For their exact relation to be finalised molecular studies may be needed, which are outside the scope of this study. With this in mind our considerations are to an extent preliminary. In his description of the species, Bremekamp (1933) noted that A. patulum is close to A. decumbens and A. molle but that no glandular hairs are present. According to the descriptions, A. patulum is distinguished from the rest by the presence of crisped hairs on stems and leaves, while A. gossweileri is distinguished by succulence of the leaves, but this seems to be an unreliable character that is not readily identifiable on herbarium specimens. Although the type, Gossweiler 61, has some description of the plant on its label, there is no mention of leaf succulence by the collector. Excluding leaf succulence, the other characters of this species are close to A. decumbens and A. molle. A. molle differs from A. decumbens in leaf indumentum, which is densely glandular-pilose on both surfaces, consisting of very slender, unequal hairs, while A. decumbens has glabrous to sparsely, short glandular-pubescent leaves. A. schinzii was provisionally placed in synonymy with A. angustifolium Emil Weber & Schinz ex Emil Weber (a synonym of A. welwitschii Hiern in this study) by Merxmüller & Roessler (1967), but this is erroneous when comparing the type specimens of both species. A. schinzii seems to be more closely related to A. decumbens and/or A. molle (see Unplaced Names in Aptosimum). No material of A. gossweileri and A. patulum was seen for this study (since these species are not recorded for Namibia), which prevented us from making any formal changes to their status here. More detailed study is necessary to clarify the relationship between A. decumbens, A. gossweileri, A. patulum, A. schinzii and A. molle. Should these names prove synonymous, A. decumbens would have priority as the oldest name (1890).

Scrophulariaceae, D. Philcox. Flora Zambesiaca 8:2. 1990

Morphology General Habit

Decumbent undershrub, widely spreading, much branched; branches up to 1 m. long, densely short-pubescent.

Morphology Leaves

Leaves (12)30–50 x 2.5–12 mm., usually rather crowded, oblanceolate-oblong, obtuse or rounded or shortly apiculate, tapering at acute base, sessile or very shortly petiolate, glabrous to sparsely, short glandular-pubescent above, denser so beneath.

Morphology Reproductive morphology Flowers

Flowers sessile or subsessile, axillary, solitary or few, clustered, bracteate.

Morphology Reproductive morphology Flowers Pedicel

Pedicel where present c. 1 mm. long.

Morphology Reproductive morphology Inflorescences Bracts

Bracts c. 5.5 mm. long, narrowly linear, acute, pubescent above and below, shortly ciliate towards base.

Morphology Reproductive morphology Flowers Calyx

Calyx 6.25–7.5 mm. long, shortly tubular with lobes 5.0–6.5 mm. long, linear-lanceolate, acute, sparsely short glandular-pubescent, very long ciliate, obscurely 1-nerved.

Morphology Reproductive morphology Flowers Corolla

Corolla purple to deep blue, tube 12–13.5 mm. long, densely short glandular-pubescent without, prominently nerved; lobes c. 4–4.5 mm. diam., broadly obovate, subequal.

Morphology Reproductive morphology Flowers Androecium Stamens Anthers

Anthers with small tuft of hairs at apex.

Morphology Reproductive morphology Fruits

Capsule c. 4.25 x 5.5 mm., laterally somewhat compressed, very broadly obovoid, retuse, densely short-pubescent, reticulate veined, margin of valves densely papillose.