Croton heterocalyx Baillon (1864: 324)

Caruzo, Maria Beatriz Rossi & Cordeiro, Inês, 2013, Taxonomic revision of Croton section Cleodora (Euphorbiaceae), Phytotaxa 121 (1), pp. 1-41 : 10-12

4. Croton heterocalyx Baillon (1864: 324) . Croton umbrinus Müller Argoviensis (1865: 86) . nom. superfl. ( Fig. 4A–E ). Type:— BRAZIL. Bahia: Jacobina, s.dat., J.S. Blanchet 3717 (holotype P [00623558]!, isotypes A!, K!, G, MO!, NY!).

Shrubs 2–4 m tall; latex clear; stellate, multiradiate and dendritic trichomes; branchlets cylindric, smooth, floccose, recovered by brownish multiradiate and dendritic trichomes. Leaves slightly discolorous, with a pair of sessile saucer-shaped basilaminar glands; lamina 3.5–15 × 2–9 cm, ovate to cordate, apex shortly acuminate, base rounded to cordate; margin serrate, with glands, upper surface pubescent, with scattered stellate trichomes, lower surface pubescent, multiradiate trichomes; venation pinnate, brochidodromous; petiole 0.6–2.5 cm long, pubescent, pale and ferrugineous stellate trichomes; stipules ca. 0.5 mm long, entire, linear-lanceolate, deciduous. Inflorescences 6–13 cm long, terminal, lax; inflorescence axis cylindric, smooth, recovered by stellate and dendritic trichomes; proximal cymules bisexual, sometimes falsely unisexual, with 1 pistillate flower and 1 staminate flower, distal cymules with ca. 3 staminate flowers; bracts ca. 4 mm long, entire, linear-lanceolate, prophylls ca. 1 mm long, linear. Staminate flowers ca. 7 mm long, cup-shaped; pedicel ca. 4 mm long; calyx ca. 3 mm long, pubescent externally, blackish stellate and multiradiate trichomes, glabrate internally; calyx lobes 5, united up to half of their lenght, ca. 1.5 mm long, entire, equal, quincuncial, ovate, apex acute, margin villose; petals ca. 3 mm long, spathulate, apex rounded, reflexed, villose at the base, simple trichomes, glabrate internally, margin villose; disk 5-segmented; stamens ca. 15, exserted from calyx; filaments linear, villose, anthers ellipsoid; receptacle villose with simple trichomes. Pistillate flowers ca. 8 mm long, flask-shaped, shortly pedicellate; pedicel ca. 1 mm long; calyx ca. 6 mm long, pubescent externally, blackish stellate and multiradiate trichomes, glabrate internally; calyx lobes 5, ca. 7 mm long, slightly united at the base, entire, equal, quincuncial, ovate to broadly-ovate, apex acute, with a band of darker trichomes in the middle portion, margin villose, midvein remarkable; petals absent; disk 5- segmented; ovary globose, velvety, stellate-porrect and multiradiate trichomes, ferrugineous; styles 3, multifid, united into a short column at the base, each one entire half of their length, then branching into 24–30 terminal arms, exserted from calyx, covered by pale stellate trichomes. Fruits ca. 1 cm long, elipsoid, smooth, stellate and multiradiate trichomes; calyx lobes accrescent; seeds ca. 7 mm long, subglobose, slightly ribbed.

Distribution and habitat: —This species occurs disjunctly in seasonally dry forests in the states of Bahia and Minas Gerais, and in “restinga” forests in Espírito Santo, from sea level to approximately 900 m elevation.

Phenology:— Flowering in January–March, August and September; fruiting in January–March, April, and August.

Taxonomic notes: — Croton heterocalyx can be recognized by its ovate to cordate leaves facing downwards on the branches, with serrate margins and branchlets densely covered by a brownish indument. Among other species of C. sect. Cleodora , C. heterocalyx is most similar to C. sphaerogynus , a species that also occurs in “restinga” forests in Espírito Santo, but differs from it by its cylindric and smooth branchlets (vs flattened and striate in C. sphaerogynus ), ovate to cordate leaves (vs ovate-lanceolate to elliptic in C. sphaerogynus ), and cup-shaped staminate flowers (vs campanulate in C. sphaerogynus ).

Another species similar to Croton heterocalyx is C. stellatoferrugineus . Both species occur in dry forests and have a similar ferrugineous indument. However, C. heterocalyx can be distinguished from C. stellatoferrugineus by differences in leaf shape (ovate to cordate in C. heterocalyx vs. narrowly ovate to ovate-elliptic in C. stellatoferrugineus ), branchlets (cylindric in C. heterocalyx vs. flattened in C. stellatoferrugineus ), and staminate flowers (cup-shaped in C. heterocalyx vs. campanulate in C. stellatoferrugineus ).

Moreno et al. (2009) studied the chemical composition and antimicrobial activity of the essencial oils extracted from the leaves of Croton heterocalyx and found great activity against the bacteria gram-positive Staphylococcus aureus and fungi Aspergillus niger and Candida albicans , showing the medicinal potencial of this species.

Selected specimens examined: — BRAZIL. Bahia: Morro do Chapéu, Rodovia BA 426 sentido Bonito, estrada de terra sentido duas barras. 11°50’41,8’’S e 41°07’16,8’’W, 923 m. s.m. Beira de Floresta Estacional Semidecidual , fl., 24 September 2006, M.B.R. Caruzo et al. 108 (HUEFS, SP) .

Figures

FIGURE 4. A–E. Croton heterocalyx. A. Flowering branch, detail of foliar stellate trichome (Caruzo et al. 108). B. Pistillate flower (Caruzo et al. 108). C. Styles arms detail (Caruzo et al. 108). D. Staminate flower (Caruzo et al. 108). E. Fruit (Caruzo et al. 108). F–K. Croton hoffmannii. F. Flowering branch (Luteyn 725). G. Pistillate flower (Luteyn 725). H. Gynoecium (Luteyn 725). I. Staminate flower (Luteyn 725). J. Stamen (Luteyn 725). K. Fruit (Mori 15388).