Mahechadendron Ariza-Cortés, Cortés-Ballén & Fern.Alonso, 2022

Ariza-Cortés, William, Cortés-B, Rocio & Fernández-Alonso, José Luis, 2022, Mahechadendron puntecascarillo (Vochysiaceae), a new genus and forest tree species from Colombia, Phytotaxa 541 (2), pp. 89-112 : 93

Mahechadendron Ariza-Cortés, Cortés-Ballén & Fern.Alonso , gen. nov. ( Figures 1–5 ).

Type species:— Mahechadendron puntecascarillo Ariza-Cortés, Cortés-Ballén & Fern.Alonso

Diagnosis:— Mahechadendron differs from other Vochysiaceae genera by the following combination of characters: axillary inflorescences in compound dichasia, compact, only developed laterally, with numerous flowers (16–30); flowers with the fourth sepal basally sacciform, villous-lanose inside, sessile, elliptic and villous petal, stamen with a villous-lanose filament, without staminodes, ovary with two ovules per locule; capsular fruit with exocarp fused to endocarp even at maturity, not brittle, with a thick and persistent central column; one seed per locule, unilaterally winged.

Description:— Trees, branchlets subopposite, decussate.Axillary cataphylls at the insertion of terminal branchlets, perulate buds prominent. Stipules minute, caducous. Leaves simple, opposite, distichous, caducous; lamina pinnately veined, villous domatia at the base of basal veins in the lower surface. Inflorescences compound dichasia, axillary, congested, main axis minute, many-flowered. Flowers asymmetrical. Calyx with quincuncial prefloration (aestivation), gamosepalous, with cup-shaped base, forming an angle of 40–60 with the pedicel, five unequal sepals, sepal 4 covering the inner whorls, base saccate, revolute in anthesis, inner surface with white villous-lanose indumentum, sepals 1 and 2 slightly unequal in size, sepals 3 and 5 lightly unequal in size, ovate, inner surface with villous-lanose indumentum; corolla with one petal inserted between sepals 3 and 5 (or slightly offset toward sepal 5), white, margin revolute in anthesis, inner surface with villous-lanose indumentum; androecium and gynoecium maturing apparently at the same time; androecium of one stamen placed offset towards sepal 3 or 5, filament with villous-lanose indumentum, anther bilocular, introrse, longitudinally dehiscent; gynoecium with superior ovary, trilocular, with white villous-lanose indumentum, placentation axile, ovules 2 per locule, style cylindrical, stigma subcapitate. Fruit a capsule, trilocular, loculicidal, trivalvous, exocarp soft, slightly tuberculate, glabrous, central column thick, persistent, and shorter than valves. Seed 1 per locule, unilaterally winged, phanerocotylar.

Etymology:—The first part of the name of this genus is dedicated to Gilberto Emilio Mahecha Vega (1942–2021), a notable Colombian Botanist, expert in dendrology, who founded the Herbarium UDBC. He was a professor of Botany and Dendrology at the Universidad Distrital Francisco José Caldas in Bogotá and trained generations of Forest Engineer students for more than two decades. Additionally, he is one of the most prolific collectors of Colombian trees and collected the Puntecascarillo for the first time in the ‘60s. The second part, “dendron” is the Greek word for tree and relates to the arborescent habit.

Figures

FIGURE 1. Illustration of Mahechadendron puntecascarillo. A. Terminal branches showing young leaves and inflorescences. B. Leaf, adaxial view. C. Flower at anthesis (lateral view) showing saccate sepal (right) and revolute petal (left), stamen and style in central position. D. Petal with revolute margins (abaxial side). E. Stamen. F. Gynoecium (lateral view). G. Ovary transverse section showing central column, two ovules per locule, and copious villous-woolly indumentum. H. Fruit at the beginning of dehiscence. I. Open fruit showing the three valves in erect-patent position and the thick central column. J. Seed. Illustration by Omar Bernal.

FIGURE 2. Mahechadendron puntecascarillo. A. Habit, tree up to 35 m tall. B. Trunk base, rhytidome, and living bark. C. Distichous leaves on terminal branches. D. Young perulate bud (arrow) on a mature branch. E. Mature leaves (abaxial side). F. Close-up of stipule (arrow) and leaf bases of young branches. G. Close-up of villous domatia at the base of secondary veins, abaxial side. H. Close-up of leaf venation. Photos A, C by Rocio Cortés-B.; B, D–F, H by W. Ariza-Cortés; G. by J.L. Fernández-A.

FIGURE 3.Mahechadendron puntecascarillo.A.Floriferousyoungbranches showing axillaryinflorescences.B.Closeup ofinflorescences showing open flowers and flower buds. C. Branch showing bark exfoliating in thin flakes and cataphylls of former perulate buds. Photos by W. Ariza-Cortés.

FIGURE 4. Mahechadendron puntecascarillo. A. Branch showing two axillary and compact inflorescences.B. Portion of an inflorescence showing an open central flower and two lateral branches. C. Open flower (lateral view). D. Flower longitudinal section showing the revolute petal and stamen (left), pistil (center), and the distally revolute saccate sepal. E, F. Ovary transverse section showing the central column, three locules, and ovules in pairs. Photos B, C, F by W.Ariza-Cortés; A, D, E by J.L. Fernández-A.

FIGURE 5. Mahechadendron puntecascarillo. A. Immature fruits erect on the branch. B. Branch showing mature fruits with different dehiscence degrees. C. Open mature fruits showing valves and central column. D. Close-up of fruit valves, externally slightly tuberculate (left), internally smooth and shiny (right). E. Seeds showing unilateral shiny wings. F. Close-up of a seed. G. Seedlings showing cotyledons and true leaves. Photos A–C, E, G by W.Ariza-Cortés; D, F by J.L. Fernández-A.