Myrcianthes cruciata M.Ibrahim & Proença, 2023

Proença, Carolyn Elinore Barnes, Faria, Jair Eustáquio Quintino De, Oliveira, Marla Ibrahim Uehbe De, Staggemeier, Vanessa Graziele, Farias-Castro, Antônio Sérgio & Sonsin-Oliveira, Júlia, 2023, Myrcianthes (Myrtaceae) revisited: a new species, a new synonym, a lectotypification and an overview of its wood anatomy, Phytotaxa 625 (1), pp. 88-97 : 90-92

1.1 Myrcianthes cruciata M.Ibrahim & Proença , sp. nov. ( Figs. 1 , 2 )

Type:— BRAZIL. Sergipe: Riach„o do Dantas . Fazenda do Dr. Delmiro , 11.02 º S, 37.05 º W, 7 June 2013, M.C.V. Farias et al. 307 (holotype ASE 0032508 !, isotypes ASE!, UB! HCV!, MAC, SAMES, SORO, HUFSJ) .

Diagnosis:— Myrcianthes cruciata is morphologically most similar to M. pseudomato from Argentina and Bolivia ( Grifo 1992). It greatly resembles it in inflorescence structure, but differs in the leaf blades that are usually obovate or oblanceolate (elliptic to narrow elliptic in M. pseudomato ) with obtuse or rounded apexes (acute in M. pseudomato ), longer peduncles, 3.5–8.5 cm (2–4 cm in M. pseudomato ), larger sepals that are 2–2.5 mm long (c. 1.5 mm long in M. pseudomato ) as well as the morphology of the embryo, which is reniform in M. cruciata ( Fig. 1 ) and strongly invaginated in the middle (almost V-shaped) in M. pseudomato (see figure 36 in Grifo 1992: 252).

Description:— Trees 12–18 m high. Bark smooth, reddish, thinly exfoliating in irregular patches. Branchlets mottled reddish and grey, thinly exfoliating. Vegetative parts essentially glabrous at maturity; petioles, leaf margins and midvein of young leaves with sparse hairs; hairs minute, whitish, strigulose. Leaves with blades 2.8–5.1 × 1.1–3 cm, slightly discolorous in live material, markedly so in dry material, obovate or oblanceolate, leaf ratio 1.5–3 times long as wide, apex obtuse or rounded, but usually abruptly narrowing into a fine, rigid tip, the tip not mucronate, base acute to attenuate, margins with a thin cartilaginous thickening, plane to minutely revolute at the base; midvein impressed on the upper surface and prominent on the lower surface; secondary venation relatively inconspicuous, c. 8–10 laterals forming an arched imperfect marginal vein; glands sparse and inconspicuous on both surfaces; petiole 4–5 mm long, delicate, canaliculate, yellowish. Inflorescences mostly 3-flowered dichasia, forks with sessile or sometimes shortly pedicellate flowers, or rarely imperfect cymes, these usually with 4–6(7) flowers; peduncles 3.5–8.5 cm long, delicate, with sparse hairs at the apical node; lateral pedicels 10–16 mm, bracteoles caducous in bud, linear, c. 1 mm long. Buds widely pyriform, 4–6 mm long; hypanthium strigulose; sepals 4, pale green in live material, 2–2.5 mm, in two slightly unequal pairs; outer pair convex-obtuse, ciliate, inner pair slightly larger, rounded, with a delicately fringed margin, both with sparse glands and densely sericeous on the inner surface; petals 4, white in live material, c. 4–5 mm diam., suborbicular, sparsely pubescent on the inner surface; disk c. 4 mm wide; stamens c. 160, 7–8 mm long, anthers pale yellow, c. 0, 5 mm, roundish, eglandular; locules 2, ovules c. 15–30 per locule, densely clustered, radiating from a shortly-stalked placenta attached to the centre of the septum; style c. 6 mm with sparse, erect hairs. Fruits wine-coloured to atropurpureous when mature, wide-ellipsoid, c. 1.4 × 1 cm, crowned by incurved sepals; seeds with a reniform embryo, the cotyledons thin, bean-like, c. 1.1 × 0.6 cm, with an external, densely pubescent, Y-shaped plumule and hypocotyl.

Wood anatomy: — Growth rings ( Fig. 3A–B ) delimited by fibre zones and discontinuous bands of axial parenchyma as a result of the higher frequency of diffuse-in-aggregates and accumulation of large vessels adjacent to the growth rings. Vessels diffuse porous, with simple perforation plates ( Fig. 3H ), exclusively solitary (> 95%) with a high density/mm² (218 µm ± 20.7), small diameter (27.3 µm ± 6.56), and vessel length (386 µm ± 114), most of them with long tails at both extremities; intervessel pits alternate, circular, vestured ( Fig. 3I ), minute (2.79 µm ± 0.33); vessel-ray pits with distinct borders, similar to the intervessel pits in size and shape throughout the ray cells ( Fig. 3I ) (2.99 µm ± 0.33), a few of them restricted to the marginal rows; deposits and tylosis in a few vessels near the pith ( Fig. 3N ); vessels in two distinct sizes but not different enough to characterize liana-type vessel dimorphism (smaller vessels 11.9 µm ± 2.6) ( Fig. 3 B;G ). Vascular tracheids apparently present, but the smaller vessels have similar diameters to the fibres, which makes the distinction difficult ( Fig. 3 F–G ). Fibres with distinctly bordered pits in both radial and tangential walls ( Fig. 3K ), very thick-walled (5.57 µm ± 0.7) ( Fig. 1B ), fibre length (769 µm ± 175). Axial parenchyma diffuse-in-aggregates forming irregular lines up to 3 cells wide and few bands, and diffuse ( Fig. 3A–B ); 5 to 8 and few more than 8 cells per strand. Rays mostly 1 to 2 cells wide (14 µm ± 3.97) up to three cells, less than 1 mm (250 µm ± 106), in high density/mm (13.9 ± 2.92), few uniseriate, some with the uniseriate portion as wide as multiseriate portion ( Fig. 3C–D ); procumbent, square and/or upright mix through the ray; body ray cells procumbent with 2 and over 4 rows of square and/or upright, and few only square and/or upright ( Fig. 3E ); disjunctive ray cells ( Fig. 3L ). Mineral inclusions absent.

Paratypes: — BRAZIL. Bahia. Vera Cruz, Berlinque , 15 April 2012, fr., Matos , E.N. 3430 ( HUEFS). Ceará. Maranguape, Serra do Aratanha , 12 April 2015, fr., Castro , A.S.F. 2867 ( EAC, HUEFS, UB!). Sergipe. Riach „o do Dantas, Fazenda do Dr. Delmiro , old fr., 28 November 2013, Lima , B. C. S., Farias , M. C. V., Matos , G. M. A. & Santos , E. 93 ( ASE!); veg., 16 October 2017, Proença , C. E. B., Farias , M. C. V, Landim , M. F., Dantas , F. S. & Santos , E. 5441 (UB!).

Etymology:—The epithet cruciata refers to the inflorescence, resembling the Latin cross; we also considered it appropriate due to the locality of one of the paratypes (Vera Cruz, Bahia, meaning true cross in archaic Portuguese) and last, but not least, by the great difficulties in collecting it.

Ecology:—Altitudes cited by collectors are 160–750 m elev. Habitats cited by other collectors are ‘subhumid forest’ and ‘forest’ but altitudes were not given.

Vernacular name (Ceará):—mameluco-louro, mameluco.

Figures

FIGURE 1. Myrcianthes cruciata. A. Habit. B. Detail of the reddish bark exfoliating in irregular patches. C. Flowering branch. D. Buds and open flowers with tetramerous calyx. E. Fruits at different stages of maturity. F. Embryo. Vouchers: A, B) Proença et al. 5441, C) Farias et al. 307, E, F) Farias-Castro 2867. Photos: A, B) F.S.Dantas, C, D) M.C.V.Farias, E) A.S.Farias-Castro.

FIGURE 2. Morphological characters of Myrcianthes cruciata M.Ibrahim & Proença. A. Flowering branch. B. Inflorescence with old flowers. C. Leaf. D. Flower bud. E. Ovary in transversal section. F. Ovary in longitudinal section. G. Cotyledon after removal of the plumule.A–F from Farias et al. 307 (ASE, UB); G from Proença et al. 5441 (UB). Pen-and-ink illustration by Claudenir S. Caires.

FIGURE 3. Branch wood Anatomy of Myrcianthes cruciata M.Ibrahim & Proença. A–B; M. Transverse section. C–D, I. Tangential section. E;J; K–L. Radial section. F–G. Macerate with vascular tracheids (arrows). H. Simple perforation plate; I. Intervessel pit. J. Vesselray pits. K. Fibre with distinctly bordered pits (arrow); L. Disjunctive ray cells (arrows); M. tyloses in vessels. Bars 100 µm.