Quercus langbianensis Hickel & A.Camus

Vietnam (Annam, where it is abundant); Cambodia; China (SE Yunnan, W Guangxi); 1000-2000 m;

7-10 m usually, but may reach 25-28 m;

7-14 x 2.5-4 cm; coriaceous; oblong-lanceolate; both sides glabrous; apex attenuate, acuminate to shortly caudate; base cuneate or oblique; margin thickened, not undulate, with small, obtuse teeth in apical 1/3; green, shiny, hairless above; hairless, nearly concolor beneath; midrib slightly raised adaxially, prominent below; 10-12 pairs of secondary veins at an angle of 40° from midrib; tertiary veins evident abaxially; petiole 1-2 cm, initially pubescent, then hairless;

acorn 2.5-3.8 cm long, 1.8-2 cm wide, obovoid to ellipsoid; pale brown, densely silky, basal scar strongly convex 1 cm wide; enclosed 1/3 by cup; cup sessile, cup-shaped, less than 1.6 cm long and 2 cm wide, very thick (wall 3 mm), rusty tomentose, with 6-9 broad, distinctly toothed, pubescent rings; stylopodium persistent ; maturing first year in September; kernel edible;

– A. Camus : n° 7; – Sub-genus Cerris, Section Cyclobalanopsis; – Section Semiserrata, sub-section Semiserratae ( Menitsky ). – Threatened (IUCN Red List Category : CR) – In 2018, H.T. Binh & al. ( PhytoKeys 95: 37–70 (2018 ) consider a “ Q. langbianensis Complex” in Vietnam and Cambodia, with 10 species : 7 species already described and often considered as synonyms of Q. langbianensis ( Q. camusiae, Q. cambodiensis, Q. baniensis, Q. dilacerata, Q. blaoensis, Q. donnaiensis et Q. langbianensis ) and 3 new species ( Q. bidoupensis, Q. honbaensis, Q. baolamensis ); actually, those 10 species share several features, morphologically speaking, which are : - mature leaf 12-17 cm long, 3-5 cm wide, margin serrate from apical 1/3 to apical 5/6, acute to acuminate apex, cuneate or attenuate base, young leaves hairy but almost hairless once mature; - acorn ovoid or globose or ellipsoid, 1/4 to 2/3 enclosed in the cup ; cup obconical or cup-shaped, with 5-9 concentric rings; The 10 species slightly differ from each other, in having other minor features, or in lacking or not some of the shared features.