Lavoisiera angustifolia Cogniaux

Martins, Angela B. & Almeda, Frank, 2017, A Monograph of the Brazilian endemic genus Lavoisiera (Melastomataceae: Microlicieae), Phytotaxa 315 (1), pp. 448-450 : 448-450

3. Lavoisiera angustifolia Cogniaux in Martius (1888: 595). Type:— BRAZIL. Minas Gerais: Serra do Cipó , Libon s.n. (holotype: C-10014588!, photos: F!, NY!; isotype, BR!).

Erect, tufted or tortuous and semi-prostrate subshrubs 7–30 cm tall. Uppermost branches quadrangular, furrowed longitudinally, essentially glabrous, mostly leafy to the base or sometimes defoliating with age at the base; internodes 1–3 mm long, with knobby thickenings that persist where a leaf has fallen away, nodes shortly and inconspicuously glandular-puberulous. Leaves sessile to subsessile, petiole flattened, 0.2–0.3 mm long, spreading to laxly or densely imbricate distally and concealing the internodes; blade 7–10 × 1–1.5 mm, coriaceous, somewhat rugose when dry, rigid, linear-lanceolate, base attenuate, apex acute and mucronate, margin beset with appressed or incurved to antrorsely spreading trichomes 0.5–0.7 mm long, slightly keeled, glabrous on both surfaces except for a few inconspicuous trichomes along the abaxial midrib, pale green to yellowish-green, 1-nerved. Flowers 5- merous, solitary or paired, sessile, terminal but becoming central. Bracts subtending the flowers 2, subsessile, with flattened petioles 0.3–0.4 mm long, blade 7–8 × 3–4 mm, ovate-lanceolate to almost ovate-oblong, inconspicuously 3–7-nerved, otherwise similar to the principal leaves. Hypanthium (at anthesis) 3 × 2.5–3 mm, campanulate to suburceolate, glabrous. Calyx tube inconspicuous, ca. 0.2 mm long; calyx lobes (at anthesis) 3.5–4 × 1.2 mm, chartaceous, triangular, subulate at the apex with an apical, spiny, glandular trichome 1.5 mm long, abaxially beset with a few glandular trichomes ca. 1 mm long, adaxially glabrous, margin entire and sparsely glandular-ciliate, cilia 1 mm long, tardily caducous, green. Petals 14 × 5 mm, pink, obovate-oblong to subspatulate, apex rounded to obtuse and shortly apiculate, base attenuate, margin entire to very shortly glandular-ciliolate. Stamens 10, dimorphic: large (antesepalous) stamens 5, filaments 4–4.5 mm long, anther thecae 2–2.5 × 0.6 mm, yellow often becoming brownish following pollination, oblong, rostrum ca. 0.6 mm long, pedoconnective 5–6 mm

48 • Phytotaxa 315 (1) © 2017 Magnolia Press

MARTINS & ALMEDA LAVOISIERA ( MELASTOMATACEAE )

Phytotaxa 315 (1) © 2017 Magnolia Press • 49 50 • Phytotaxa 315 (1) © 2017 Magnolia Press

MARTINS & ALMEDA long, appendage ca. 1.5 mm long, ± rounded; small (antepetalous) stamens 5, filaments 3–4 mm long, anther thecae 2 × 0.6 mm, yellow, oblong, rostrum 0.6 mm long, pedoconnective 2 mm long, appendage ca. 1 mm long, rounded to somewhat bilobed. Ovary 5-locular, 1/2 inferior, style 6–8 mm long, slightly curved, glabrous, stigma not seen. Fruiting hypanthium (including calyx lobes) 7–8 × 2.5–3 mm, campanulate. Capsule (at maturity) 4–5 mm long, globose, brown, enveloped by the persistent hypanthium and calyx lobes, dehiscing from the base to the apex. Seeds 0.65–0.75 × 0.41–0.45 mm, oblong, brown, periclinal cell walls of the testa vaguely concave (foveolate), the raphal zone about 50% the length of the seed. Chromosome number unknown.

Illustration:— Figure 19 .

Phenology:—Flowering time unknown; fruiting in November.

Distribution and habitat:—Endemic to the Serra do Espinhaço in Minas Gerais (from Serra do Cipó and Serra do Córrego das Congonhas) where it was reportedly collected in wet fields at an unspecified elevation. Figure 20 .

Conservation status:— This little-collected species is known to us from the type and two other collections, all of which were collected on the Serra do Cipó. None of these collections have exact locality information on the labels and all of the collections are old. Since so much of the Serra do Cipó is prone to frequent fires coupled with severe recent drought we are recommending a classification of Critically Endangered ( CR): B2 ac(iv) .

Discussion:— Lavoisiera angustifolia is one of the rarest and most distinctive species in the genus. In general aspect it is almost ericoid in appearance with short (7–10 mm) linear-lanceolate leaf blades that are laxly or densely imbricate on distal branchlets and ± concealing the internodes. Other diagnostic characters include the 1-nerved leaf blades that are glabrous except for the sparsely ciliate margins and the few inconspicuous ± appressed trichomes along the abaxial midrib. In addition, the flowers are 5-merous, the hypanthia are glabrous, the calyx lobes are moderately covered with spreading glandular trichomes and the ovary is 5-locular.

Among congeners with a 5-merous flower and 5-locular ovary the only one that superficially approaches L. angustifolia in habit is the rarely collected L. tetragona . This latter species is readily distinguished by its shorter leaves (4–5 mm), essentially glabrous, ovate to oblong-ovate leaf blades with shallowly crenulate margins (at least distally) and a prominent keeled midrib abaxially. Its calyx lobes are also glabrous on both surfaces with inconspicuous sessile-glandular crenulate margins.

Additional specimens examined:— MINAS GERAIS: Mpio. Santana do Riacho, Serra do Cipó, Lund s.n. (P!); Mpio. Caeté, Serra do Córrego das Congonhas, Mendes Magalhães 2276 (BHCB ex BHMH!, RB!).

Figures

FIGURE 19. Lavoisiera angustifolia. A. Habit. B. Branch with terminal flower. C. Abaxial leaf surface. D. Adaxial leaf surface. E. Abaxial bract surface. F. Hypanthium and calyx lobes. G. Ovary cross section. H. Petal with margin detail (right). I. Ventral view of antesepalous stamen. J. Ventral view of antepetalous stamen. K. Seed. (Based on: A–K, Libon s.n., C.)

FIGURE 20. Distributions of Lavoisiera angustifolia, L. belinelloi, L. bradeana, L. punctata, L. sampaioana, L. scaberula, and L. tetragona.