Carlowrightia texana Henrickson & T.F.Daniel

  • Authority

    Daniel, Thomas F. 1983. Carloivrightia (Acanthaceae). Fl. Neotrop. Monogr. 34: 1-116. (Published by NYBG Press)

  • Family

    Acanthaceae

  • Scientific Name

    Carlowrightia texana Henrickson & T.F.Daniel

  • Type

    Type. United States. Texas. Val Verde Co.: along Hwy. 163, 6 mi N of Juno, 19 Jun 1957, Correll & Johnston 18254 (LL!, holotype; GH!, NY!, SMU!, isotypes).

  • Description

    Species Description - Erect to decumbent, suffrutescent perennial to 3.5 dm high, arising from a woody caudex to 11 mm in diameter or a woody rhizome to 3 mm in diameter. Older stems quadrate to terete or with irregularly fissured bark, 1-2 mm in diameter, glabrate. Younger stems green, quadrate to terete, multistriate, 0.5-1.5 mm in diameter, evenly and more or less densely pubescent, the trichomes eglandular, retrorse, 0.1-0.5(-1.0) mm long (strigose), often with a sparse and inconspicuous understory of stipitate glands, 0.1-0.3 mm long. Leaves ascendent to horizontal, petiolate; petioles (1-)3-7(-20) mm long, pubescent like younger stems; laminas (deltate) broadly ovate to orbicular when larger, narrowly ovate to elliptic when smaller, (2.5-)6-16(-42) mm long, (1.5-)3.0--1.0(-33.0) mm wide, mostly 1.0-3.5 times longer than wide, truncate to rounded to acute (or frequently oblique) at base, acuminate to acute (to rounded) at apex; margins flat, entire to minutely undulate, strigose-ciliate; surfaces strigose (often with a sparse, inconspicuous glandular understory as on the younger stems), especially along the veins; several orders of venation evident, though often obscured on the upper surface. Reduced dichasia solitary or opposite at the nodes, sessile to short pedunculate in leaf axils, the peduncles 0.5-3.0 mm long (often subtended by an aborted or poorly developed shoot from a second axillary bud), rarely the dichasia borne in the axils of bracts (2-5 mm long and 1-3 mm wide) on an elongate, terminal, spicate axis to 8 cm long; flowers 1-3 (or more) per dichasium, each sessile to short (to 1 mm long) pedicellate, subtended by 2 bractlets. Bractlets foliaceous, usually petiolate, the petioles 1-5 mm long, narrowly ovate to elliptic-lanceolate, 2-12 mm long, (0.7-)2.5-5.0 mm wide, pubescent like leaves. Secondary bractlets (if present) narrowly elliptic to linear, 2-3 mm long, 0.5-1.0 mm wide. Calyx (2.5-)3.0-6.0 mm long, the outer surface pubescent like leaves, the inner surface sparsely sericeous with appressed trichomes to 0.5 mm long; tube 0.5-1.0 mm long; lobes subulate, 2-5 mm long, 0.3-0.5 mm wide at base. Corolla bilabiate, white with maroon veins on the lobes, lacking a papillate, yellow eye on the upper lip, 5.5-7.0 mm long, pubescent on the outer surface with trichomes 0.1-0.2 mm long; tube 1.5-3.0 mm long, 1.0-1.5 mm in diameter; upper lip obovate-spatulate, 3.5-5.0 mm long, 1.8-2.7 mm wide, emarginate at apex; lower lip 4.0-6.0 mm long, the lateral lobes spreading or horizontally oriented, obovate-elliptic, 3.5-5.5 mm long, 1.8-2.8 mm wide, the lower lobe oblanceolate, conduplicate-keeled, 4.0-4.5 mm long, 1.5-2.0 mm wide. Stamens 3.3-5.0 mm long, filaments white, 2.2-4.0 mm long, 0.2 mm wide at base, pubescent, especially near the base with trichomes 0.1-0.2 mm long; anthers maroon turning black, thecae 0.5-1.0 mm long. Disc 0.2-0.4 mm high. Style 3.0-6.0 mm long, glabrous. Stigma lobes 0.2 mm long. Capsules 7.5-12.5 mm long, glabrous; stipe 2.0-4.5 mm long; head flattened, 5.5-8.5 mm long (including a terminal beak 1.0-1.5 mm long), 4.0-5.2 mm wide; retinacula 1.8-2.1 mm long. Seeds usually 4 per capsule, flat, obliquely cordate in outline, 4.2-6.0 mm long, 3.5-4.9 mm wide, rounded to acute at apex; testa (smooth) papillose; margins entire. Flowering. Carlowrightia texana begins to flower in the early spring (March), reaches peak flowering during the spring and summer, and continues to flower into November.

  • Discussion

    Discussion. Carlowrightia texana is the only species of Carlowrightia known to have colored veins on each of the petal lobes. It also differs from all the species of section Mexicana by lacking a papillate, yellow eye on the upper lip of the corolla. Henrickson and Daniel (1979) described this species and noted its close relationship with C. torreyana. Indeed these species, which often occur sympatrically, are the only two known to hybridize in nature. In both instances, the hybrids were intermediate in most morphological characters and occurred in disturbed habitats. Near Del Rio, Texas, plants of C. torreyana (Daniel 128, 180) were found growing in partial shade on limestone ledges along a stream and plants of C. texana(Daniel 125, 126, 176, 177) were found growing on a grassy roadbank. Hybrids (Daniel 127, 178) were located growing under an overpass, across the stream and adjacent to the roadbank. They resemble shade forms of C. texana (Daniel 126, 177) in habit, but have longer, more flexuose trichomes. In addition, the corolla has a faint yellow eye with scattered papillae on the upper lip as well as maroon veins on the lower petal lobes. The corolla of C. torreyana has a prominently papillate, yellow eye which is absent in C. texana. A hybrid population, probably a hybrid swarm, in Huasteca Canyon near Monterrey, Nuevo Leon, was located growing in and along a gravel road. Both species and the hybrids were growing in exposed habitats and resembled one another in growth form. Differences between the species were detectable in pubescence, corolla coloration, and seed margins. The hybrids were intermediate in the diagnostic characters, and although the field specimens showed considerable pollen stainability, a subsequent generation of these hybrids grown from seed in the greenhouse exhibited greatly increased percentages of pollen abortion. The presence of an intermixed population of parents and hybrids, all with a relatively high degree of fertility, would allow backcrossing and may help to explain some of the variation encountered in specimens of both C. texana and C. torreyana.

    Despite its occurrence in nature with C. serpyllifolia, C. mexicana, C. parvifolia, and C. glandulosa, no hybrids have been found between C. texana and any of these species, although the artificial hybridizations indicate that most are possible.

    The extremes of habit and leaf size in C. texana are largely attributable to environmental factors such as exposure and moisture. Figure 29 shows the differences between sun and shade forms of C. texana from the same locality in a relatively wet and a relatively dry year.

    Distribution and Ecology: Carlowrightia texana is the most widely distributed species of the genus in the Chihuahuan Desert and even ranges out of the desert region into southern and central Texas. Its range extends from the south Texas plains and adjacent Mexican scrublands northward into the central Texas prairies, westward across the Edwards Plateau into the Chihuahuan Desert of Trans-Pecos, Texas and southeastern New Mexico, and southward through Chihuahua, Coahuila, and Nuevo Leon to the southern boundary of the Chihuahuan Desert in San Luis Potosí (Fig. 26). The species commonly grows in sandy or gravelly soils in the mesquite woodlands of the south Texas plains at elevations of 25 to 300 meters. In the desert, it is found on limestone flats and hills or in the calcareous alluvium of arroyos at elevations to 1700 meters. Throughout its range, C. texana invades disturbed habitats and is especially common in old fields, along fences, and beside paved highways.

  • Distribution

    United States of America North America| New Mexico United States of America North America| Chihuahua Mexico North America| Coahuila Mexico North America| Nuevo León Mexico North America| San Luis Potosí Mexico North America|