Charianthus dominicensis Penneys & Judd

Description

Description Author and Date: D. Penneys, Oct. 2011, modified from Penneys & Judd, 2005.

Type: Dominica. St. George Parish: Morne Micotrin, Cable & Wireless trail that begins after the bridge and 100 ft beyond the park boundary. Lower limits of elfin forest. 15° 20’ 38”N, 61° 18’ 97”W, 1045 m, 5 June 2000, D. S. Penneys 1315 (holotype: FLAS!; isotypes: A!, MO!, NY!).

Description: Evergreen shrubs or small trees to 5 m high; bark gray to brown, smooth to shallowly, longitudinally fissured; young twigs quadrangular, becoming terete with age, reddish or green, becoming brown, (glabrous) occasionally with unicellular hairs, usually with multicellular multiseriate setae, or with a dense indumentum of conspicuous, scurfy, whitish, matted, multicellular, stellate hairs that may congeal to form a crust that can abscise in plates, the stellate hairs (0.11)0.18 - 0.30(0.38) mm in diameter, twigs finally glabrous; nodes somewhat swollen, (4.40)5.6 - 6.88(7.34) mm in diameter, a slightly expanded, usually conspicuous interpetiolar ridge present, with pubescence similar to that on twigs, as well as multicellular multiseriate setae, often with thickened bases, in a dense ring around the node and petiole attachment points, the setae (1.27)1.60 - 2.57(3.10) mm in length. Leaf blade coriaceous (very rarely chartaceous), ovate to elliptic or widely elliptic, (6.0)7.6 - 9.80(12.1) cm long, (4.3)4.6 - 6.1(8.4) cm wide, usually curved abaxially near margin, apex obtuse (acute), the tip acuminate (long-acuminate) and often inrolled to such a degree so as to contact the abaxial leaf surface; base obtuse, sometimes with small cordate lobes barely overlapping petiole apex; adaxial surface of young blades with scurfy stellate hairs and unicellular hairs, mature leaves generally glabrous, sometimes with unicellular hairs and scurfy stellate hairs, occasionally appearing as punctuations, especially near base; abaxial surface of young blades with stellate hairs, irregular white, scurfy stellate hairs that form a dense mat covering the blade and veins (falling from blade with age, but usually remaining on veins), also unicellular hairs, multicellular uniseriate hairs, and multicellular multiseriate setae along margin, the scurfy stellate hairs (0.16)0.24 - 0.38(0.48) mm in diameter, mature leaves with dense white, scurfy stellate hairs at base and on veins throughout, also on blade but fewer, unicellular hairs mostly on veins, scars of fallen hairs appear as yellowish-tawny dots on blade, scurfy stellate hairs (0.14)0.19 - 0.33(0.48) mm in diameter; margin (± plane) distinctly revolute, slightly crenate in distal 1/2 of blade; venation basal, rarely somewhat decurrent, with 2 or 3 pairs of secondary veins, and 1 pair of inconspicuous submarginal secondary veins, the tertiary veins (25)27 - 35(38), intergrading with quaternary veins at base and apex. Petiole (1.0)1.3 - 3.3(3.4) cm long, shallowly canaliculate, multicellular multiseriate setae along sulcus above, scurfy stellate hairs like those on blade also mixed in with the setae (these occur throughout on younger petioles, deciduous from underside with age), multicellular multiseriate setae (0.97)1.30 - 2.16(2.60) mm long. Inflorescence terminal, cymose, corymbose, (3.9)5.5 - 7.4(8.9) cm long, (3.0)3.6 - 6.7(9.0) cm wide, with 3 - 4(5) orders of branching, the caducous bracts to ca 2.3 mm long; peduncle (0.5)0.8 - 2.2(2.8) cm long, first internode above peduncle (0.9)1.13 - 2.40(3.0) cm long, first lateral internode (1.29)1.4 - 2.5(4.3) cm long, the flowers (26)35 - 60(73) per inflorescence. Pedicels (2.54)2.80 - 4.54(5.00) mm long, with unicellular uniseriate and scurfy, whitish, stellate hairs (0.16)0.19 - 0.31(0.35) mm in diameter. Hypanthium (3.94)4.34 - 4.67(4.80) mm long as measured from base to torus, (3.87)3.94 - 4.27(4.80) mm wide, the indumentum of unicellular hairs (sparse) and white scurfy stellate hairs, dense near pedicel attachment, progressively sparser approaching calyx lobes, the epidermis of the hypanthium frequently obscured by the indumentum white scurfy stellate hairs (0.08)0.11 - 0.22(0.29) mm in diameter, the portion of hypanthium free from ovary (1.25)1.41 - 1.53(1.88) mm long; inner hypanthium smooth to granular textured, often with indistinct ridges, torus to calyx apex length (1.72)2.04 - 2.82(2.94) mm, torus to calyx notch length (0.18)0.21 - 0.85(1.28) mm. Calyx lobes (1.32)1.50 - 2.19(2.44) mm long, (2.66)3.07 - 3.60(3.69) mm wide, lobes broadly triangular, the indumentum similar to that of hypanthium, the external calyx teeth (0.25)0.33 - 0.72(1.35) mm long, bluntly rounded, with apex directed upwards. Petals bright red to dark red (reddish-orange), irregularly orbicular to broadly orbicular, (6.34)6.60 - 7.34(8.0) mm long, (5.88)6.27 - 7.67(7.34) mm wide. Stamens (9.75)9.87 - 10.75(10.88) mm long; filaments cream, 7.09 - 7.75 mm long, with proximal filament segment (0.69)0.81 - 1.14(1.38) mm wide, distal segment (0.56)0.60 - 0.69(0.78) mm wide; anthers yellow, (2.66)2.72 - 3.00(3.16) mm long, (0.65)0.67 - 0.85(0.88) mm wide, longitudinal slits (1.94)2.19 - 2.44(2.54) mm long. Ovary (2.35)2.60 - 3.19(3.74) mm long, (1.75)1.88 - 2.75(2.91) mm wide, style cream, (7.60)10.0 - 13.75(14.75) mm long, (0.67)0.81 - 0.95(1.19) mm wide. Berries 5 - 7 mm in diameter. Seeds 0.70 - 0.95 mm long, 0.46 - 0.72 mm wide. See Figs. 2, 8, 9.

Habitat and Distribution: Charianthus dominicensis is endemic to the volcanic peaks of Dominica at elevations from 750 to 1,300 meters (Fig. 9). The typical habitat is elfin woodland, but the species may occasionally be found in the transition zone to montane thicket (Beard 1944). Charianthus dominicensis forms a limited hybrid zone with C. corymbosus (Rich.) Cogn. in the vicinity of Freshwater Lake and Boeri Lake. Charianthus dominicensis - formerly treated as C. purpureus var. rugosus Hodge (Hodge 1941) and listed as such in the IUCN Red List of Threatened Plants - is considered to be a rare plant (Walter and Gillett 1998).

Phenology: Collections of this species in bud, flower, and fruit have been made during every month of the year with the exceptions of April, September, and October - months for which no collections have been examined.

Taxonomy and Systematics: In his treatment of the genus, Hodge (1941) treated this species as a variety and noted, erroneously, that the scurfy, whitish, matted stellate hairs represent the only character by which it is separable from other geographical variants of Charianthus purpureus (sensu Hodge). In the current revision, with a larger set of available specimens, a broader and more detailed examination of the characters was possible. This improved material yielded additional differences between Hodge’s varieties, and justifies the recognition of the populations of this taxon on Dominica at the specific level (Penneys and Judd 2004). Charianthus dominicensis differs from C. grenadensis and C. purpureus in that several reproductive structures are consistently smaller, e.g., petals (6.34)6.60 - 7.34(8.0) mm long vs. (8.38)9.0 - 10.88(12.0) mm long in the latter two taxa, stamens (9.75)9.87 - 10.75(10.88) mm long vs. (18.5)19.5 - 24.0(26.0) mm long, and the style (7.60)10.0 - 13.75(14.75) mm long vs. (20.0)20.5 - 26.0(27.0) mm long (see also Penneys 2001). The specific epithet refers to the distribution of this species, which is endemic to the Lesser Antillean island of Dominica.

Map Distribution

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Objects

Images

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Charianthus dominicensis: SEM of whole seed. (image/jpeg)

Charianthus dominicensis: SEM of whole seed. (image/jpeg)

Charianthus dominicensis: SEM of seed testa. (image/jpeg)

Charianthus dominicensis: SEM of seed testa. (image/jpeg)