Phymatidium hysteranthum Barb.Rodr.

De Brito, A. (2007). A Taxonomic Revision of the Genus Phymatidium (Orchidaceae: Oncidiinae). Kew Bulletin, 62(4), 529-560. Retrieved from http://www.jstor.org/stable/20443388

Type

Brazil, Rio de Janeiro, Barbosa Rodrigues s.n. (Lost). Lectotype, here designated: Barbosa Rodrigues' original illustration which appeared in his Iconographie des orchidées du Brésil, vol. 6, plate 315, fig. A (Library of Rio de Janeiro Botanical Garden!), reproduced in Sprunger et al. (1996: 443).

Morphology General Habit

Plant up to c. 35 mm tall, usually forming a intricate clump

Morphology Roots

Roots several, terete, thick, papillose, somewhat flexuous, usually quite long and forming a cluster of several adnate roots

Morphology Stem

Stem up to c. 15 mm long, usually inconspicuous and branched near the base

Morphology Leaves

Leaves up to c. 30 x 1.5 mm, falcate, somewhat twisted, variable in cross-section in the same specimen and the same leaf, 3-angled, semi-terete, oval to semi-oval, slightly sheathing and shortly decurrent at base, the apex acute

Morphology Reproductive morphology Inflorescences

Inflorescences several, up to c. 100 mm long, racemose, few- to c. 20 flowered; peduncle up to c. 45 mm long, 3-angled in cross-section, flexuous, covered by several, fleshy,  usually somewhat 3-angled in cross-section, falcate, narrowly ovate-lanceolate to linear-subulate sterile bracts, up to c. 10 x 0.5 mm, acute; rachis up to c. 55 mm long, usually slightly zig-zag, 3-angled in cross section; floral bracts similar to the sterile ones, decreasing in size towards the apex of inflorescence

Morphology Reproductive morphology Flowers

Flowers usually resupinate, white with green centre

Morphology Reproductive morphology Flowers Pedicel

Pedicel 3 - 5.5 mm long, somewhat twisted, slightly angular, inconspicuously papillose on the angles

Morphology Reproductive morphology Flowers Gynoecium Ovary

Ovary 0.5 - 1 mm long, slightly three-keeled

Morphology Reproductive morphology Flowers Calyx

Lateral sepals 3 - 4 x 0.5 - 1.5 mm, narrowly ovate to somewhat oblong, slightly falcate, strongly reflexed, acute to obtuse, abaxially slightly carinate Dorsal sepal 2.5 - 3.5 x 0.5 - 1.5 mm, oblong-lanceolate, ovate or narrowly ovate, usually somewhat lanceolate and falcate, reflexed, somewhat arching, slightly concave, acute to slightly obtuse, abaxially weakly carinate

Morphology Reproductive morphology Flowers Corolla

Lip 3 - 4 x 2 - 4 mm, broadly unguiculate; blade cordiform, acute, deflexed, usually rather convex; margins dentate to erose at middle of the lip, becoming entire towards the base and the apex; base provided with a large, thick, concave, broadly ligulate callus which is glandular within and equals or slightly exceeds the length of the claw of the lip Petal 3 - 4 x 0.6 - 1.2 mm, ovate to narrowly ovate, oblong or lanceolate, usually somewhat oblique with slightly waved margins, convex, slightly reflexed and arching upwards, acute to obtuse, abaxially slightly carinate

Morphology Reproductive morphology Flowers Column

Column 2 3.5 mm long (excluding the tabula infrastigmatica), clearly sigmoid, sulcate underneath; apex of the column somewhat recurved, usually somewhat apiculate, auriculate, the auricles glabrous, somewhat obliquely broadly ovate to slightly semi-lunate when spread, running from approximately the same level as the rostellum and diminishing in breadth towards the apex of the column, the margins of the auricles usually somewhat erose to crenulate; stigmatic cavity small, ovate, placed at the base of the column; rostellum very short, curved forwards; tabula infrastigmatica 0.7 - 1 x 0.6 mm, laterally excavated in side view, with a small, raised, thick, somewhat cordiform-sagittate to broadly lanceolate callus sitting on a shorter, thick, usually semi-globose to ovoid platform; anther 1.5 mm long, narrowly ovate, operculate, distinctly beaked, incurved, with a small tooth on each margin near apex, which is shortly recurved and emarginate; pollinia arranged in two superposed unequal pairs, the superior pair clavate, the inferior somewhat obovoid; stipe c. 1.2 mm long, narrowly spathulate, curved forward at the base, the apex weakly emarginate; viscidium small, somewhat rounded and concave

Morphology Reproductive morphology Fruits

Capsule c. 3 x 2.5 mm, subglobose, obscurely ridged, the pedicel 2.5 - 4.5 min long.

Distribution

Brazil: São Paulo, Rio de Janeiro, Minas Gerais and Espírito Santo.

Ecology

Epiphytic on small branches of shrubs and trees in forest. Also found in disturbed areas and orchards. Alt. 0 - 1400 m.

Note

Although similar in habit to Phymatidium aquinoi, P. hysteranthum is closely related to P. delicatulum and its allies. The strongly reflexed sepals and arching petals together with column and anther morphology are very distinctive and readily separate it from all other species of Phymatidium. This species was misidentified as P. delicatulum in Senghas (1995). The specific epithet derives from the Latin hysteranthus, meaning leaves produced later than the flowers. However, this phenomenon has not been reported in the genus Phymatidium.