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(Last Modified On 6/15/2016)
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Description:
Plants (80–)150–200(–300) mm high. Corm globose, 10–15 mm diam., developing several large cormels at base; tunics of coarsely netted fibres, thickened and forming woody claws below, accumulating with age and forming collar up to 20 mm long around base of stem. Stem erect, flexuous or flexed outward only above sheath of second leaf, unbranched, (1.5–)2.0–2.5 mm diam. below spike. Cataphylls dry and papery, reddish brown. Leaves 4(5), lowermost inserted below ground, blade reaching base of spike or not, ± dry at flowering, linear, elliptic or terete in section, 70–170 × 0.5–1.5(–2.0) mm, leathery, with 3 ± equally distinct veins or with main vein slightly more distinct, not thickened or raised when fresh but prominent when dry, upper 3(4) leaves cauline with lower 2 inserted on lower 1/3 of stem and sheathing for ± 1/2 length, sheaths usually shortly imbricate, blades 50–70 mm long, uppermost leaf a little distant from lower leaves and well separated from spike, entirely sheathing or with short blade 20–50 mm long. Spike erect, densely 7–15(–30)-flowered; bracts imbricate for ± 1/2 length, 8–10(–12) mm long and ± two internodes long, outer entirely brown and leathery, obtuse or truncate (rarely apiculate), conspicuously and closely veined, with narrow membranous margins, inner 1/2 to 3/4 as long as outer, bifid, ± membranous with narrow brown zones along veins. Flowers ± patent, purple to violet with dark blotches and streaks on longitudinal veins and especially midline; perianth actinomorphic; tube slightly curved, (7–)8–10(–15) mm long, funnel-shaped, usually exserted 2–6(–10) mm beyond bracts, rarely just included; tepals oblanceolate, subequal or inner slightly broader, spreading and slightly cupped, (10–)11–17 × 3–6 mm. Stamens unilateral, ± declinate, sometimes weakly so and then ± central; filaments 8–10 mm long, exserted ± 6–8 mm from tube, usually flexed sharply upwards apically; anthers all facing upwards, usually white (rarely purple), 4–6 mm long; pollen white (rarely brown when anthers purple). Ovary obovoid, 2.0–2.5 mm long; style ± deflexed to lie beneath stamens, dividing opposite middle of anthers, branches 3–5 mm long, divided to near base. Capsules ovoid, ± 6 mm long. Seeds subglobose- or ellipsoid-angled, ± 2 mm long, chalaza truncate, brown, testa colliculate. Flowering time: late Nov.– early Jan
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South African Province:
Western Cape
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Distribution and ecology:
the only species of Thereianthus on the Cape Peninsula, T. bracteolatus occurs from the Peninsula and Stellenbosch along the coastal ranges of the Hottentots Holland, Kogelberg and Klein River/Babilonstoring Mtns to Elim in the east, with isolated records from near Caledon (Drayton Siding) and the lower slopes of the Riviersonderend Mtns above Greyton (Figure 13). Somewhat surprisingly, the species has not been recorded from the Caledon Swartberg. There is an early record, Zeyher 1068 (SAM), from the Twenty Four Rivers Mtns near Porterville, but the species has never been re-collected here and as this collection is a mixed one that includes a stem of T. longicollis, which is known from this location, the association of T. bracteolatus with the locality is probably an error. The species is locally common after fire on sandy flats and lower slopes below 1 000 m, although plants will also flower in cleared places along roads in the absence of fire. The distribution of T. bracteolatus largely overlaps with that of T. spicatus, with the notable exception of the Cape Peninsula where only T. bracteolatus is found, but T. spicatus favours more stony sites and often heavier soils. We have encountered both species growing adjacent to each other at Kogelberg, with T. bracteolatus on damper soils and flowering in December and T. spicatus immediately adjacent on rocky slopes and flowering in January.
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Diagnosis:
Thereianthus bracteolatus is unmistakeable when seen alive, with linear terete or elliptic leaves, 0.5–1.5(–2) mm diam., and terete or elliptic in section, and dense spikes of sideways-facing, deep purple or violet flowers with curved perianth tube 7–10(–15) mm long, and relatively long, unilateral, declinate stamens. The flowers, which lack nectar-guides, have darkly pigmented veins, giving them a characteristic blotched-striate appearance. Although Lewis noted in here 1941 account fo the genus that the branching pattern of the veins was distinctive for the species, this difference is not evident in all plants. Like other species in the genus, each tepal has three primary longitudinal veins but unlike other species, the lateral veins are often only branched in the basal half so that the tepals appear to be ± parallel-veined for most of their length. In the other species the veins are not darkly pigmented and thus not evident, and the lateral longitudinal veins are ± evenly branched throughout their length.
Perianth tube length is somewhat variable, usually 8–10 mm but 10–15 mm long in an isolated population at Drayton Siding east of Caledon (Goldblatt 394). The anthers and pollen are usually white but plants from the Silvermine area of the Cape Peninsula have purple anthers with brown pollen. Another isolated population, from the lower slopes of the Riviersonderend Mtns above Greyton (Esterhuysen 20763), has stamens that are less obviously declinate than usual but matches the species in vegetative and other floral characters, including the distinctive tepal venation. This population may repay further consideration.
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General Notes:
the smooth leaves and especially the declinate stamens (but not the characteristic tepal venation) are both shared with Thereianthus bulbiferus from gravelly flats between Malmesbury and Paarl. This species has pale to mid-blue flowers with distinct white blotches at the base of each tepal, and shorter filaments, 6–8 mm long. Most characteristically, the plants develop a cluster of cormels in the axil of the lower leaf, whereas cormels in T. bracteolatus are developed at the base of the parent corm. Although T. bracteolatus is sometimes confused with T. spicatus, especially in the dried state when details of the perianth coloration and stamen orientation are obscured, the two are readily distinguished by the difference in leaf texture: leathery and terete or elliptic in section without raised veins in T. bracteolatus versus plane and ribbed or corrugate with raised veins in T. spicatus. Living plants of T. spicatus are readily separated by their blue (rarely white or pink) flowers with white markings on the lower three tepals outlined with a purple chevron and lacking darker venation, the ± straight or distally curved perianth tube, 12–25 mm long, and the much shorter, arcuate filaments, 3–4 mm long.
History: the second species of Thereianthus to be described after T. spicatus, T. bracteolatus was named in the genus Gladiolus by French biologist J.P.B. Lamarck in 1788 from specimens said to have been collected by naturalist and draughtsman Pierre Sonnerat, who could only have collected this material in 1773, on his voyage to Isle de France (now Mauritius). This name was overlooked by the English botanical artist and engraver, Henry Andrews, who described Ixia punctata from plants cultivated in London that had been sent to collector and botanical patron G. Hibbert from the Cape of Good Hope. In continental Europe, the species was described under the name Gladiolus triticeus for a third time a few years later by Thunberg (in 1807), based on his own collections. At the time Thunberg expressed doubt as to whether his species was truly different from G. spicatus L. (i.e. T. spicatus) and must have appreciated the similarity between these species, ultimately to be treated in a separate genus. J.G. Baker (in 1892) subsequently treated Thunberg’s name as a variety of Andrew’s species, which had by now been transferred to Watsonia as W. punctata (Andrews) Ker Gawl. The nomenclature was clarified by Lewis, who correctly identified Lamarck’s name as the earliest for the species, and also established the genus Thereianthus for plants until then treated as subgen. Beilia of Watsonia.
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Pollination:
the purple or violet to blue flowers with a relatively short perianth tube are evidently adapted to pollination by various nectar-feeding bees.
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