Mitracarpus carajasensis E. L. Cabral, Sobrado & E. B. Souza, 2013

Cabral, Elsa L., Sobrado, Sandra V. & Souza, Elnatan Bezerra de, 2013, Three new species of Mitracarpus Zucc. (Rubiaceae) from Brazil, Candollea 68 (1), pp. 139-146 : 140

Mitracarpus carajasensis E. L. Cabral, Sobrado & E. B. Souza , spec. nova ( Fig. 1 , 2 A-B).

Typus: BRAZIL. Pará: Canaã dos Carajás, 6°23’1’’S 50°23’10’’W, 753 m, 16.III.2009, fl fr, V. T. Giorni, P. L. Viana, L. M. Versieux, L. M. Garcia, L. V. C. Silva & D. S. Silva 196 (holo-: BHCB!; iso-: CTES!).

Mitracarpo parvulo affinis, sed ab eo habito erecto (vs caespitoso), caulibus glabris (vs pubescentibus), foliis 20- 29 mm longis et 1-2 mm latis (vs foliis 7-15 mm longis et 1-4 mm latis), setis stipularibus 4-5 (vs 5-7), 2(-4) bracteis involucralibus foliaceis glomerulis inflorescentiae quatruplo longioribus (vs 4 bracteis inequalibus in glomerulis terminalibus), seminibus dorso lineis 2 cruciformiter depressis (vs sine depressione dorsali), differt.

Simple or sparsely branched, erect herb, 15-25 cm tall. Stems subcylindrical to quadrangular, glabrous, internodes 2.5-5 cm long. Leaves sessile, leaf-blades 20-29 × 1-2 mm, linear, glabrous, apex attenuate, base acute, margins revolute, scaberulous, secondary veins obscure. Stipules 1-1.5 mm long, ribs and bristles pilose basally violet, bristles 4-5, ca. 1-1.5 mm, linear, glabrous. Inflorescence a terminal glomerule, 5-6 mm wide, subtended by 2(-4) foliaceous bracts, 4 times longer than the glomerule, 1-2 axillary glomerules also present. Flowers with hypanthium 0.5- 1 mm long, glabrous, calyx 4-merous, 2 large lobes, 1.3-2 mm long, subtriangular, exceeding the corolla tube, greenish, margins ciliate; 2 small lobes, ca. 0.5-1 mm long, hyaline; corolla white, 2-3 mm long, infundibuliform, tube 1.3 mm long, inside with moniliform hairs around the tube’s base, papillose inside and outside. Stamens subsessile, filaments 0.1-0.2 mm long, anthers 0.5 mm. Style 1.5-2 mm long, style-arms 0.1-0.3 mm long, papillose. Capsule 1 × 1 mm, glabrous. Seeds obovoid, 0.6- 1 × 0.6 mm, light brown; the ventral face with an X-shaped groove covered with whitish granular excrescences and the dorsal face with central cruciform depression and angular depressions caused by the extensions of the ventral groove, testa reticulate-foveate with irregularly outlined cells ( Fig. 3 A-D).

Distribution and habitat. – Brazil, in Pará State, in the microregion of Canaã dos Carajás and Parauapebas. It grows in rocky field on “canga’’. The canga vegetation is characterized by the patches of saxicolous scrubby vegetation on the iron outcrops, usually on mountain summits ( SECCO & MESQUITA, 1983).

Notes. – Mitracarpus carajasensis is related to M. parvulus K. Schum. , the corolla tube being shorter than the lobes of the calyx. Both have opposite leaves and lack brachyblasts. However, the latter is a cespitose herb, branched from the base, with marked pubescence and seeds without depressions on the dorsal faces.

Paratypi. – BRAZIL. Pará: Canaã dos Carajás, 6°21’30.69’’S 50°23’58.91’’W, 700 m, 18.V.2010, L.C.V. Silva&al.880 ( BHCB, CTES); 6°20’34.32’’S 50°25’24.04’’W, 700 m, 19.V.2010, L. C. V. Silva & al. 889 ( BHCB, CTES); 6°23’48.94’’S 50°22’21.84’’W, 728 m, 22.III.2012, A. J. Arruda & al. 773 ( BHCB, CTES); 6°17’2.38’’S 50°20’13.13’’W, 580 m, 22.III.2012, A. J. Arruda & al. 779 ( BHCB, CTES); 6°22’32.10’’S 50°22’58’’W, 715 m, 22.III.2012, P. B. Mayer & al. 1163 ( BHCB, CTES); Serra da Bocaina , 6°19’35.39’’S 49°58’5.53’’W, 697 m, 20.IV.2012, A. J. Arruda & al. 960 ( BHCB, CTES); Parauapebas, 6°11’1.63’’S 50°7’47.31’’W, 701 m, 23.III.2012, P. B. Mayer & al. 1166 ( BHCB, CTES); 6°4’23.74’’S 50°11’35.08’’W, 554 m, 24.III.2012, P. B. Mayer & al. 1195 ( BHCB, CTES); 6°9’13.18’’S 50°10’20.79’’W, 693 m, 25.III.2012, P. B. Mayer & al. 1229 ( BHCB, CTES).

Figures

Fig. 1. – Mitracarpus carajasensis E. L. Cabral, Sobrado & E. B. Souza. A. Habit; B. Stipular sheath; C. Leaf-blade; D. Flower; E. Corolla; F. Style and stigma; G. Calyx; H. Dehiscent fruit; I-K. Seed; I. Dorsal view; J. Ventral view; K. Lateral view. [Giorni & al. 196, BHCB] [Drawing: L. Simón]

Fig. 2. – Mitracarpus carajasensis E. L. Cabral, Sobrado & E. B. Souza: A. Habit; B. Terminal glomerule. Mitracarpus fernandesii E. L. Cabral, Sobrado & E. B. Souza: C. Habit; D. Pseudoverticillate leaves; E. Terminal glomerule,1 pair of bracts located between the flowers are shown; F. Flowers of the axillary glomerule. [Photos: A-B: P. L. Viana; C-F: E. B. Souza]

Fig. 3. – Seed morphology (SEM-graphs). Mitracarpus carajasensis E. L. Cabral, Sobrado & E. B. Souza: A. Ventral view; B. Lateral view, notice the extensions of the ventral groove and the dorsal face depression; C. Dorsal view; D. Detail of reticulate-foveate testa. Mitracarpus federalensis E. L. Cabral, Sobrado & E. B. Souza: E. Ventral view; F. Lateral view, notice the extensions of the ventral groove; G. Dorsal view; H. Detail of testa of the lateral face, showing the hydrated papillas; I. Detail of testa of the dorsal face, showing the dehydrated papillas. Mitracarpus fernandesii E. L. Cabral, Sobrado & E. B. Souza: J. Ventral view; K. Lateral view, notice the extensions of ventral groove and dorsal depression; L. Dorsal view; M. Detail of reticulate-areolate testa of the dorsal angle; N. Detail of reticulate testa of the dorsal depression [Scale bars: A-C, E-G, J-L: 0.25 mm; D, H-I, M-N: 50 µm]. [A-D: Giorni & al. 196, BHCB; E-I: Fonseca & Alvarenga 4582, IBGE; J-N: Souza & al. 1737, HUV]