Monographs Details: Ouratea mazaruniensis A.C.Sm. & Dwyer
Authority: Maguire, Bassett. 1989. The Botany of the Guayana Highland- Part XIII. Mem. New York Bot. Gard. XIII: 1-127.
Family:Ochnaceae
Description:Species Description - Shrub or small tree 1.8 m tall. Leaves coriaceous or subcoriaceous, elliptic to elliptic-oblong, rounded or obtuse at the sometimes emarginate apex, subcordate, rounded, or obtuse at base, (5-)7-12.5 c m long, 2.5-5 c m wide, uniformly obscurely crenulate with 6-9 crenulations per cm, lower surface with subimpressed, subalveolate reticulation, the lateral nerves slightly more prominulous, upper surface with the tertiary venation obsolete and lateral nerves slightly manifest. Petioles 1-5 c m long. Inflorescence paniculate, relatively few-flowered, 6-10 c m long, 4-6 c m wide, the 3-5 lateral axes 3-6 c m long; pedicels 7-10 m m long at anthesis, 12-13 m m long in fruit. Flower bud ovoid, obtuse, (5-)6- 7(-9) m m long; sepals oblong-lanceolate, obtuse, or minutely apiculate, 6-7.5 m m long, 2.5-3.5 m m wide. Petals broadly obovate, rounded at apex, 6-7.5 m m long, 5-7 m m wide. Anthers 5- 6 m m long, transversely strongly mgulose. Gynophore 1-1.2 m m long in anthesis, 1V2 times longer

Distribution and Ecology - W e t savannas and rocky ground, Kaieteur Savanna and Mazamni River drainages, Guyana, 360-700 m.

Discussion:

Specimens examined. GUYANA. Kaieteur Savanna, 365 m, 2 Sep 1937, Sandwith 1293 (K, NY); same locality, 4 Sep 1937, Sandwith 1350 (K, NY); upper Mazamni drainage, Jan 1939, Pinkus 278 (NY); Ambam River (Kako tributary), upper Mazamni drainage, nr. Mount Haiamatipu, 600 m, 2 Feb 1939, Pinkus 185 (holotype NY); sedge bogs on fringe of bush islands, Kaieteur Savanna, Kaieteur Plateau, 2 May 1944, Maguire & Fanshawe 23147, 23147-A, 23147-B {NY); savanna and low savanna forest nr. Kaieteur Falls, Kaieteur Savanna, 425 m, 4 Mar 1962, Cowan & Soderstrom 20477 (NY, US).

The obscurely crenulate leaf margins, short petioles, longer pedicels, shorter, less branched inflorescences, upper leaf surface with prominently elevated nerves and tertiary venation, and the lower surface with more prominent nervation and with the tertiary venation conspicuously subparallel, subhorizontal, and elongated are characteristic of O. mazaruniensis. They clearly diflferentiate as such the above cited specimens, some of which were originally misidentified as O. roraimae Engl