Quercus langbianensis

Quercus langbianensis is an uncommon oak tree species in the family Fagaceae. It is placed in subgenus Cerris, section Cyclobalanopsis, the ring-cupped oaks. These differ from other Quercus groups in that they have acorns with distinctive cups: usually with substantial rings, made-up of scales that have grown together. This species can be found in sub-tropical and tropical seasonal forests of Vietnam.

Synonymy
A number of species names, previously considered synonyms, are now considered to be valid. These very similar species are considered by Binh, Ngoc et al. (2018) to be a species complex; more information is available in Oaks of the World.

Other species names previously listed here were:
 * Quercus baniensis A.Camus - Vietnam
 * Quercus blaoensis A.Camus - Vietnam
 * Quercus cambodiensis Hickel & A.Camus [synonyms Q. langbianensis subsp. Cambodiensis, Q. auricoma ] - Cambodia
 * Quercus camusiae - Vietnam and China (mostly Yunnan).
 * Quercus dilacerata Hickel & A.Camus - Vietnam
 * Quercus donnaiensis A.Camus - Vietnam
 * Quercus pachyloma [synonym Cyclobalanopsis pachyloma  var. mubianensis ] - native to S. China and Taiwan.

Description
Quercus langbianensis is an evergreen tree that reaches a height of up to 15 m. The leaves measure 70-140 (up to 170) x 25–40 mm, elliptical-lanceolate to oblanceolate, leathery and glabrous on both sides, with margins having numerous small teeth that are obtuse, wavy near the apex: which is acuminate to slightly  caudate; petioles are 15–20 mm and hairless.

The acorns are sub-globose approximately 17–20 mm, covered with fine silky hair (sericeous), pale brown and ripening by September; scars are approximately 10 mm in diameter and convex. Their styles are persistent about 2 mm in diameter. Superficially, the cups are bowl-shaped, 8 x 20–25 mm approximately, enclosing 1/2 or 2/3 of the acorn. Outside and inside the reddish, tomentose acorn has a wall about 3 mm thick. The bracts are formed by 5 to 7 rings, with whole margins.