Monotes pearsonii Bancroft 1936
Creators: name: Meerts, Pierre
name: Rougelot, Quentin
name: Sosef, Marc
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Malvales
Dipterocarpaceae
Monotes
Monotes pearsonii

description: 12. Monotes pearsonii Bancroft (1936a: 44)   
 Type: — ANGOLA. In open forest in lower part of pass leading down to Lubango, l 785 m, May 8, 1909, Pearson 2649 (holo-: K! [barcode K000240339]; iso-: BRLU! (fragm.), FHO).   
Small tree up to 6 m high; young twigs more or less pubescent, glabrescent. Leaf: petiole 10–16(–21) mm long, 1.5 mm in diameter, shortly pubescent; blade very variable in shape even on the same branch, obovate to elliptic or ovate-elliptic, (4.5–)6–11.5 × (1.5–)2.5–6.5(–7) cm, base rounded, truncate or slighlty cordate, apex rounded or emarginate, more rarely obtuse; secondary nerves in 10–14 pairs, distally curved and tangent to leaf margin, short intercalary nerves often present; upper surface markedly reticulate, with indumentum just perceptible, soft to the touch, persistent, with a mixture of short simple and geminate more less erect, curved or flexuous hairs (0.2–0.4 mm) and numerous yellow glands, becoming brownish when dry, secondary and tertiary nerves generally impressed; lower surface discolorous, whitish to greyish, with reticulum well visible though not very prominent, often with a reddish tinge; areoles covered with small stellate hairs and reticulum with curled hairs (ca. 0.5 mm long), costa with fulvous indumentum of very short curled hairs. Inflorescence of narrow axillary racemose cymes of 1–4 cm long and 1–1.5 cm wide, with rachis densely tomentose. Flower: pedicel ca. 2 mm long, sepals broadly ovate-triangular, ca. 3 × 2.5 mm; petals ca. 9 × 3 mm, 8-nerved; anthers with conspicuous appendage. Fruit slightly depressed, ca. 18 mm in diameter; wings (materials from Angola) up to 8 × 2 cm, red, unguiculate at base, acute at apex.  
 Illustrations: — Figs. 3S, 4R, 8E.   
 Distribution in D.R. Congo: —Upper Katanga (first record for D.R. Congo).   
 Distribution elsewhere: — Angola; taxon knwown from few collections.   
 Habitat and ecology: —Wooded slopes on shallow rocky soil.   
 Other representative specimens examined:—D.R. CONGO. Upper Katanga: Kisenge-Kapolo, forêt sur sol léger à Brachystegia longifolia, 18 August 1956, Duvigneaud & Timperman 2364 (BRLU!); Entre Mukumbi et Swambo, forêt sur terre ocre à Brachystegia “Sandwe” et Monotes sp., 28 December 1959, Duvigneaud 4798M (BRLU!); Kasekelesa, restes de la forêt primitive entre les carrières de Mn, 24 January 1960, Duvigneaud 5233M (BRLU!)); Nzilo, forêt-verger à Monotes div. sp. enrochée, sur phyllades kibariennes, 27 January 1960, Duvigneaud 5268M3 (BRLU!).   
 Discussion:— M. pearsonii was previously known from only three collections in southern Angola. ca. 1000 km south-west of the nearest Congolese localities. The new collections, though without fruits, have the characteristic pattern of pubescence of the type. They allow a more complete assessment of the variation in the species. The Katangan specimens are indeed much more variable in leaf shape than the Angolan ones; leaf shape sometimes varies on the same branch. In particular, some Katangan collections break down one of the supposedly diagnostic traits of the species, i.e. the possession of obovate leaves. However, we were not able to find any diagnostic trait to justify treating the Katangan material as a distinct taxon. Our circumscription of M. pearsonii is thus broader than previously defined based on just the scarce materials from Angola. The type specimen has very large unguiculate fruit wings, but M. pearsonii has not been collected in fruit in D.R. Congo.   
 At first sight, M. pearsonii is deceptively similar to some forms of M. hypoleucus var. caloneurus. However, M. pearsonii differs in the upper surface of the leaf being markedly reticulate and with hairs longer and stiffer, just perceptible to the touch. The hairs of M. pearsonii are ca. 12 μm in diameter, with a well-developed lumen of 4 μm; those of M. caloneurus are variable in thickness along their length (5–12 μm) and with the lumen almost obliterated at places.   
 References:— Bancroft (1936a: 44; 1937: 141; 1939a: 354, 378); Catarino et al. (2013: 272); Figueiredo & Smith (2008: 67); Lebrun & Stork (1991: 144).
description: Published as part of Meerts, Pierre, Rougelot, Quentin & Sosef, Marc, 2017, Revision of the genus Monotes (Dipterocarpaceae) in D. R. Congo, with implications for Angola and its distinction from Marquesia, pp. 151-205 in Phytotaxa 308 (2) on pages 192-193, DOI: 10.11646/phytotaxa.308.2.1, http://zenodo.org/record/13701270