Asclepias minutissima appears most similar to A. aurea (Schltr.) Schltr. but differs in the campanulate rather than rotate to reflexed corolla, the ascending disposition of the corona rather than radiating from the column in A. aurea, the absence of the well-developed distal tongue to the corona of the latter species, and the shorter peduncles (1–3 cm rather than (3)5–14 cm in A. aurea).

Angola. Moxico Province: Mussuma plains, 50 km NE of Lumbala, Zambezi drainage, 13°45'49"S, 021°43'25"E, fl. 7 December 2019, D.Goyder & F.Maiato 9204 (holotype: K (K001334259); isotypes: INBAC, LUBA, PRE).

Perennial herb with a single erect stem arising annually from a small napiform tuber, latex white; stems 8–15 cm long, minutely pubescent along two lines. Leaves sessile, 3–7 × 0.05 cm, filiform with inrolled margins, glabrous. Inflorescences terminal or extra-axillary, umbelliform, with 4–5 erect flowers; peduncles 1–3 cm long, minutely pubescent; pedicels c. 1 cm long, minutely pubescent. Sepals 1–1.5 mm long, narrowly to broadly triangular, glabrous. Corolla campanulate, lobes 3.5–4 × 1.5 mm, oblong, green or white, glabrous on both faces. Corona lobes 2–3 mm long, cucullate, lacking an apical tongue, pinkish cream or white. Anther wings 1 mm long. Stylar head flat. Follicles not seen. (Fig. 1).

Figure 1. 

Asclepias minutissima A habit B flower C corona lobe D gynostegium E pollinarium. Drawn by Margaret Tebbs from Richards 17269.

Known from a single collection in eastern Angola and one in NW Zambia. The Angolan population consisted of several scattered individuals on a broad open sandy plain just above the water table. Both the Angolan and the Zambian localities are on Kalahari sand deposits, and the Angolan collection was associated with common geoxylic suffrutices of the region such as Parinari capensis Harv., Syzygium guineense (Willd.) DC. subsp. huillense (Hiern) F.White, Eugenia malangensis (O.Hoffm.) Nied., Lannea gossweileri Exell & Mendonça subsp. gossweileri and Cryptosepalum sp. aff. mimosoides Welw. ex Oliv. Altitude 1100–1300 m. (Map 1).

Map 1. 

Known distribution of Asclepias minutissima (eastern Angola and NW Zambia).

Asclepias minutissima is known from two localities some 350 km apart, but is inconspicuous and easily overlooked and is likely to be more common than the herbarium records suggest. Both localities are in nutrient-deficient sandy environments unsuitable for agriculture, and with little threat of habitat transformation as human settlements are few and far between. The new species is therefore provisionally assessed as Data Deficient.

Zambia. Mwinilunga District, 16 km along road from Matonchi Farm, 11°39'S, 24°03'E, fl. 17 November 1962, Richards 17269 (K).

Only three species of Asclepias were reported from Angola by Goyder (2008). Asclepias baumii Schltr., known only from the type collection which was destroyed in Berlin, is almost certainly synonymous with A. aurea, as is A. radiata S.Moore (Goyder 2009). Asclepias randii S.Moore is also present. Following the transfer of Odontostelma Rendle to Asclepias by Goyder (2009), A. minor (S.Moore) Goyder, also occurs in the country. All of these species occur in scattered populations with few individuals, as is common for Asclepias and allied genera in tropical Africa. As a result, they tend to be collected very infrequently and few herbarium records exist for any of them in Angola.

Asclepias randii is a much more robust plant than the other species and has pubescent stems and leaves. A. aurea and A. minor are glabrous and are slender herbs. Asclepias minor has a corona which is much reduced, not even reaching the base of the anther wings and has a short ventral appendage. So the species most similar to our new collection appears to be the highly variable A. aurea, which occurs across Namibia, southern Angola, Zambia, the Katanga region of the D.R.Congo, Zimbabwe, northern provinces of South Africa, Eswatini (Swaziland) and Lesotho (Goyder 2009).

Asclepias aurea has rotate to reflexed corolla lobes, corona lobes which radiate from the column and are extended into a long distal tongue, and longer peduncles. In addition to the rather subtle morphological characters that distinguish the new species from A. aurea, its ecological requirements, close to the water table on leached Kalahari sand, are probably also significant. Asclepias aurea occurs on richer soils. The new taxon was mentioned by Goyder et al. (2020: 276) in a note under the related A. aurea but the Angolan (type) collection was cited incorrectly as Goyder & Gonçalves 4809.

Cochlospermum adjanyae differs from all African species of the genus in possessing palmatisect rather than palmatifid or lobed leaves, with discrete leaflets rather than partially connate lobes.

Angola. Moxico Province: Lungué-Bungo valley, 50 km S of Munhango, near Lungué-Bungo bridge, 12°36'50"S, 018°47'59"E, fl. 20 November 2019, D.Goyder & A.Gomes 9002 (holotype: K (K001334241); isotypes: INBAC, LUBA, PRE).

Geoxylic suffrutex forming diffuse but discrete patches several metres across; above-ground stems 10–20 cm tall, sub-erect, glabrous, burned off in the dry season. Leaves palmate with (4–)5 leaflets; stipules c. 3 mm long, narrowly triangular; petioles (2–)4–6 cm long, glabrous except for a minute rusty pubescence at the junction with the leaflets; leaflets reducing in size from the central leaflet to the lateral and basal ones, central leaflet 3–5 cm long, 1.2–2 cm wide, elliptic to slightly obovate, acute or occasionally obtuse apically, the base somewhat cuneate, margins serrate at least in the upper half, glabrous except for a minute rusty pubescence at the junction with the petiole adaxially. Inflorescences minutely rusty-puberulent, terminal on the leafy shoots, with 1–3 flowers; peduncles 2.5–3 cm long; sepals subequal, 11–15 × 7–8 mm, broadly ovate or elliptic, rounded apically, minutely rusty-puberulent and with occasional dark streaks, the outer pair more deeply coloured than the inner three; petals c. 3 × 2–2.3 cm, obovate, rounded or slightly emarginate, bright yellow with linear red streaks. Stamens numerous (80+), yellow; anthers c. 5 mm long, straight or weakly curved, apical pore 0.5–1 mm long. Ovary c. 2 mm in diameter, glabrous. Fruit not seen. (Figs 2, 3).

Figure 2. 

Cochlospermum adjanyae A, B habit C flower D ovary and style E stamens. Drawn by Margaret Tebbs from Goyder & Gomes 9002.

Figure 3. 

Cochlospermum adjanyae. Photographed by Chris Boyes at the type locality.

Found only once in flower in grassland rich in geoxylic suffrutices on deep Kalahari sand. Material in bud had been encountered, but not collected, the day before in a similar grassland some 15 km to the NW along with the new species of Baphia described below and other geoxyles such as Sclerocroton oblongifolius (Müll.Arg.) Kruijt & Roebers, Parinari capensis, Entada arenaria Schinz and Englerophytum magalismontanum (Sond.) T.D.Penn. The fact that this conspicuously flowered species was seen only on the November 2019 expedition and not on earlier ones through the same valley system (late rainy season; early and mid-dry season) suggests that populations are highly localised and that the flowering period is short, at the end of the dry season, and perhaps dependent on rainfall following fire. Altitude 1285–1340 m. (Map 2).

Map 2. 

Known distribution of Cochlospermum adjanyae.

The specific epithet honours Adjany Costa who was part of the core National Geographic Okavango Wilderness Project headwaters team from the first expedition in 2015 until she left to pursue academic studies at Oxford University in 2019. Initially, she supported freshwater fish specialists Paul Skelton and Ben van der Waal, recording and preserving freshwater fish diversity from the Cuito source to the Delta, before developing the communities programme with Chris and Steve Boyes. She was a National Geographic Young Explorer, starred in the National Geographic documentary film “Into the Okavango”, and was awarded the United Nation’s Young Champions of the Earth Prize for Africa in 2019.

While Cochlostemum adjanyae is known from a single locality, these geoxyle-rich grasslands are not currently threatened as this nutrient-poor sandy environment is not conducive to agricultural development. The environment does not support many human settlements, which are few and far between. The species is probably best assessed as Data Deficient.

Cochlospermum Kunth is a pantropical genus of around 16 species of trees, shrubs and geoxylic suffrutices, or if expanded to include the herbaceous neotropical genus Amoreuxia DC., 20 species. C. noldeae Poppend. from NE Angola, C. macnamarae Hislop, K.R.Thiele & Brassington and C. arafuricum Cowie & R.A.Kerrigan from Australia (Poppendieck 2004 (see nomenclatural note below), Hislop et al. 2013, Cowie and Kerrigan 2015) were described after Poppendieck’s (1980) monograph of the group where he had recognised 12 species. Irrespective of the circumscription of the genus, molecular evidence presented by Johnson-Fulton and Watson (2017) supports the monophyly of Cochlospermum subgenus Cochlospermum sensu Poppendieck (1980), which comprises two species from Central and South America (C. vitifolium (Willd.) Spreng. and C. regium (Mart. ex Schrank) Pilg.), and all the paleotropical species. Johnson-Fulton and Watson (2017) argue that the geoxylic habit evolved just once from an ancestral arboreal lifeform – all but one of the African taxa are geoxyles, together with a single neotropical species, C. regium, from cerrado (savanna) regions of Brazil, Paraguay and Bolivia. The remaining species are trees or shrubs.

Species of Cochlospermum subg. Cochlospermum have a single apical pore to the anthers, and in addition to growth form, can be distinguished by leaf indentation or lobing, indumentum, and the position and timing of flowers on the shoots. A collection made in the geoxyle-rich Lungué-Bungo valley grasslands of Moxico in November 2019 is unique in the African species in having palmatisect leaves, divided to the base rather than being merely lobed. The only other taxon in the subgenus with this leaf character is the nomenclaturally illegitimate C. gillivrayi Benth. subsp. gregorii (F.Muell.) Poppend., an Australian tree. The Angolan material is described as a new species. It is perhaps closest morphologically to C. wittei Robyns from the Upemba region of Katanga. Cochlospermum wittei is also associated with savanna and woodland on sand plateaux (Poppendieck 1980) but these are nearly 1000 km to the NE of the Lungué-Bungo grasslands.

Differs from E. tubulascens (Briq.) M.Ashby in the little-branched habit, the sessile rather than petiolate and linear rather than elliptic leaves, the fewer-flowered (4–6-flowered rather than 6–10-flowered) verticils in the inflorescence, the pale violet rather than pinkish white flowers and the longer calyx (fruiting calyx 8–9 mm long rather than 5.5–6 mm).

Angola. Moxico Province: Confluence of Cuito River and its 1^st tributary, the Kalua River, c. 65 km SSW of Munhango, 12°44'55"S, 018°21'16"E, fl. 20 Oct. 2016, D.Goyder & F.Maiato 8762 (holotype: K (K001333409); isotypes: INBAC, LUBA).

Aromatic perennial suffrutex with few stems arising from a thick woody rootstock; stems erect, 15–30 cm tall, branched near the base, square in section above, more rounded below, pubescent with both glandular and eglandular hairs. Leaves verticillate, ascending, sessile, linear and folded along the midvein, 2.5–5 cm long, 0.1–0.2 cm wide, pubescent. Inflorescence lax with 4–6-flowered verticils 1.5–2.5 cm apart; bracts lanceolate or narrowly ovate, 3.5–4.5 mm long; pedicels 1–5 mm long, longer in lower verticils. Calyx 5 mm long at anthesis, pubescent with spreading hairs and sessile glands, posterior lip purplish; fruiting calyx 8–9 mm long. Corolla pale violet, 8–10 mm long; tube 6–7 mm long, straight, parallel-sided, dilating at the throat. Filaments c. 0.5 mm long, glabrous or pilose. Ovaries pubescent at apex. (Fig. 4).

Figure 4. 

Endostemon palustris A habit B flower C opened corolla showing androecium and gynoecium D base of gynoecium showing three of the four nutlets and the gynobasic style E individual nutlet F calyx G indumentum. Drawn by Margaret Tebbs from Goyder & Maiato 8762.

Known only from the type collection close to the source of the Cuito River. It was found towards the upper edge of a marsh fringing the river. (Map 3).

Map 3. 

Known distribution of Endostemon palustris (star), and of the related species E. tubulascens (cross).

Although known from a single locality, Endostemon palustris occupies a habitat that is extensive within the upper catchment of the Cuito and its tributaries. The area is not threatened with agricultural development being both nutrient poor and many kilometres from any human habitation, but with so little information the species is provisionally assessed as Data Deficient.

Endostemon N.E.Br. is an isolated genus of 20 species within the tribe Ocimeae, with two centres of endemism – Angola and the Horn of Africa. It can be recognised within the Orthosiphon Benth. group of genera by its short, villous staminal filaments, an expanded shield-like base to the style, and pollen with alternating wide and narrow mesocolpia (Paton et al. 1994; Ryding et al. 2003; Paton et al. 2004). With the exception of E. tereticaulis (Poir.) M. Ashby which is in Endostemon sect. Oblongi Ayob. ex A.J.Paton, Harley & M.M.Harley, all of the Angolan species fall within Endostemon sect. Endostemon. This section is characterised by a relatively short calyx tube with an open glabrous throat, and the form of the lateral calyx lobes – the posterior margins of these lobes are not extended towards the upper lip of the calyx. Endostemon tubulascens, to which this new species is compared, appears largely restricted to the high escarpment zone around Lubango, Huíla Province, Angola.

Most similar morphologically to B. massaiensis Taub., from which it can be readily distinguished by its geoxylic lifeform, flowering and fruiting at ground level on short, prostrate above-ground shoots, and the villous suture of the keel petal.

Angola. Moxico Province: tributary of the Lungué-Bungo River 42 km SSE of Munhango, 12°31'34"S, 018°40'13"E, fl. 22 October 2016, D.Goyder & F.Maiato 8772 (holotype: K (K001333933); isotypes: INBAC, LUBA).

Geoxylic suffrutex forming large patches; above-ground shoots prostrate, 5–10 cm long, pubescent, arising from extensive woody below-ground stems. Leaves unifoliolate; stipules linear, 3–4 mm long, densely pubescent with silvery hairs; petiole 3–5 mm long, pulvinus barely apparent; leaflet narrowly obovate-oblong and generally folded along the midvein, 4–6 cm long, 1–2 cm wide, obtuse apically, tapering somewhat towards the base, ± glabrous except for the major veins beneath. Inflorescences with an indumentum of greyish or golden hairs; flowers 1–3 in sessile or subsessile axillary fascicles; pedicels 15–20 mm long; bracteoles 1–2 mm below the calyx, caducous. Calyx 7–10 mm long, spathaceous. Petals white, the standard with a yellow triangular mark towards the base; standard 10–12 × 8–10 mm, emarginate; wings c. 10 × 2 mm; keel 10–12 × 2.5–3 mm, lower suture villous distally. Stamens 10, free. Ovary 6–9 mm long, villous, with a glabrous upturned style. Legume c. 7 cm long, c. 1.5 cm wide, brown. Seeds c. 10 mm long, dark brown or black. (Figs 5, 6).

Figure 5. 

Baphia arenicola A habit B bud C open flower D standard petal E wing petal F keel petal G androecium H stamen J gynoecium K fruit. Drawn by Margaret Tebbs from Goyder & Maiato 8772 (flowering material) and Gomes & Maiato 161 (fruit).

Figure 6. 

Baphia arenicola. Photographed by David Goyder at the type locality.

Flowering in October and November in the late dry season or at the onset of the rains; fruiting in February. Known from three sites, the first in the Lungué-Bungo river system of western Moxico Province at an elevation of around 1350 m, the second in the Cusseque River system of Bié Province some 200 km to the SW of the Moxico site at around 1530 m, and the third just over the watershed into the Cacuchi River valley which drains into the Rio Cuchi and is around 1540 m. The three sites are similar topographically, with broad fossil river terraces and sandy alluvial deposits rich in geoxylic suffrutices (Gröngröft et al. 2013b, Revermann et al. 2013, Goyder et al. 2018). (Map 4).

Map 4. 

Known distribution of Baphia arenicola (central Angola).

Baphia arenicola is known from three localities, two of which have vouchered herbarium collections. TFO project made many unvouchered observations of the plant in the Cusseque and Cacuchi River valleys and it is clear that there are extensive populations of this species. There are no significant threats to these nutrient-poor grasslands rich in geoxylic suffrutices as the environment is not conducive to agricultural development. B. arenicola is therefore provisionally assessed as Least Concern.

Angola. Bié Province: Cusseque, TFO core site relevé 23324, 13°41'53"S, 017°06'43"E, fl. 29 October 2011, Finckh 132753 (HBG, K); Cusseque, TFO core site relevé 23349, 13°41'53"S, 017°07'48"E, fl. 2 November 2011, Revermann 132895 (HBG, K); Cusseque village, Chitembo, 13°43'21"S, 017°05'53"E, fr. 17 February 2014, Gomes & Maiato 161 (LUBA); Cusseque 15 September 2019, Finckh 145383A (HBG, LUBA); Cusseque, 28 January 2020, Finckh 145352B (HBG, LUBA).

Baphia Afzel. ex G.Lodd is a genus of around 50 species of woody legumes which has diversified across tropical Africa (Soladoye 1985, Goncharov et al. 2011). A single species extends its distribution to the white sands of NW Madagascar, with a second species endemic to that region (Stirton and Du Puy 1992). Members of the genus are recognised readily by their unifoliolate leaves, free rather than united stamens, and flat, dark brown seeds lacking an aril. Seeds of other genera of the unifoliolate Baphioid clade of Lewis et al. (2005) are globose, arillate, and bicoloured or otherwise brightly coloured (Cheek et al. 2014). Baphia species occur in evergreen forest, thicket and woodland with several species restricted to white sands (Stirton and Du Puy 1992, Brummitt 2007, Mackinder and Clark 2012, Cheek et al. 2014). While most species are shrubs or small trees, B. aurivellerea Taub. from NE Angola and western DR Congo can be suffrutescent, but this species still possesses erect woody shoots 20 cm to two metres above ground level. In contrast, an undescribed species encountered in central Angola flowers at ground level on short, prostrate above-ground shoots and is here formally described as Baphia arenicola.

Most floral characters invite comparison with the locally common woodland species B. massaiensis, with its spathaceous calyx split longitudinally down a single line, bracteoles longer than wide and positioned shortly below the apex of the pedicel, glabrous staminal filaments, and pubescent ovary. The keel petal which is somewhat villous along its line of fusion, however, suggests links to B. bequaertii De Wild., another miombo woodland species of the region. Preliminary molecular analyses by one of us (PM) places the new taxon close to the latter species, with estimated divergence times from B. bequaertii less than 1 mya. Divergence times from B. massaiensis, on the other hand, are estimated to be between 11 and 27 mya.

Vangueria fulgida is a small woody species with conspicuous orange flowers. It can form single-stemmed plants to 1.5 m in height, but over much of its range it behaves as a geoxylic suffrutex, forming patches of much shorter above-ground shoots that are burned off each year. It is found mostly on Kalahari sands and is widely distributed across Angola, western Zambia, Botswana, Namibia and Zimbabwe (Bridson 1998; Figueiredo 2008a, b).

Molecular studies of the tribe Vanguerieae A.Rich. ex Dumort. (Lantz and Bremer 2004; Lantz and Bremer 2005; Razafimandimbison et al. 2009) have shown that the species of Ancylanthos Desf. are showy members of Vangueria Juss., and combinations under the latter were made in Lantz and Bremer (2005). However, Vangueria rubiginosa (Desf.) Lantz is a later homonym of V. rubiginosa K.Schum. (Schumann 1897: 457) and is therefore illegitimate.

The earliest synonym listed by Bridson (1998), Ancylanthos ferrugineus Welw. (Welwitsch 1868a: 29), must be treated as a nomen nudum because “very pretty” does not constitute a validating description under the International Code of Nomenclature for algae, fungi, and plants (Turland et al. 2018). No specimen was cited but, as Welwitsch was writing about the Pedras Negras of Pungo Andongo, Angola it can be inferred that Welwitsch 3159 from this region is probably this plant. Welwitsch’s second account of the Pedras Negras (Welwitsch 1868b), makes no mention of the plant.

Ancylanthos bainesii Hiern (1877) and A. fulgidus Welw. ex Hiern (1877) were published simultaneously and the epithets are both available under Vangueria, so either could be used as a basionym for a new combination to replace the illegitimate V. rubiginosa (Desf.) Lantz – we have chosen to use A. fulgidus described from the Huíla Plateau of Angola, a name more widely adopted than A. bainesii (Hiern 1898; Schumann 1903: 390; Durand and Durand 1909: 271; De Wildeman 1910: 424, 1913: 153, 1925: 204; Robyns 1928). We designate the LISU specimen bearing Welwitsch’s handwritten note as the lectotype of this name.

Hiern (1877) cited two specimens in his description of Ancylanthos bainesii. One, without a locality, was just cited as “T.Baines!”. The second is the Chapman & Baines collection labelled “lat. 23°”. Goyder (2016b) drew attention to problems localising Chapman & Baines’ collections particularly those labelled lat. 23° – if taken literally, this would imply they were collected near the Namibian coast E of Walvis Bay, but as this is desert and therefore unsuitable habitat for most of the species bearing these labels, it is much more likely that, given the well-documented route of the expedition, they originated in northern Botswana. Robyns (1928: 329) effectively lectotypified the name by citing the unlocalised “T.Baines” collection as the type.