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Paradombeya Notes

Paradombeya burmanica Stapf
Paradombeya sinensis Dunn

Malvaceae Info (Home)
Partial Synonymy of Asian Dombeyoid Genera

Introduction

Paradombeya is a genus of shrubs belonging to subfamily Dombeyoideae of the angiosperm family Malvaceae sensu APG. In spite of the name it does not appear to be closely related to Dombeya, and might instead, as the original author throught, belong to a group of Asian genera including Pentapetes and Corchoropsis. However it has also been placed in Bombacaceae.

There are two [1], or possibly three [2], species. The third species would be Paradombeya multiflora Gamble, but apart from a mention in a checklist of the plants of Burma [3] I can find no information about this. I suspect that it the same as Paradombeya burmanica. The two definite species were described on consecutive pages of Icones Plantarum [4]

Description

The foliage of Paradombeya is alternate, stipulate, and sessile or shortly petiolate. The blades are lanceolate, with a rounded base, an acuminate apex, and serrate margins.

The flowers are borne in fasiculate cymose clusters in the leaf axils. The flowers possess articulated pedicels. There is an epicalyx of 2 or 3 bracteoles placed near the articulation. The calyx is divided into five lobes which are joined only at the base. It is valvate in aestivation. The sepals (lobes) are glabrous. The corolla is composed of 5 yellow, asymmetrically broadly ovate petals, with truncate apices. The stamens are grouped into 5 groups of 3 alternating with 5 ligulate staminodes. The filaments are fused at their base, forming a short staminal tube. The ovary is sessile, with 2 or 5 locules. There are two colateral ovules in each locule, but usually only a single seed is produced in each locule. The fruit is a stellate-puberulent, subglobose capsule, the locules of which are easily separated. The seeds are oblong-ovoid and dark brown in colour.

The pollen is triporate, echinate and spheroidal [5].

Paradombeya burmanica Stapf.
Thai ปอเชียงดาว

Paradombeya burmanica is the type species. It is found in Myanmar (Burma), Thailand [1] and Yunnan [6, 7].

The foliage of Paradombeya burmanica is alternate, stipulate and shortly petiolate. The petioles are up to 4mm long.. The blades are lanceolate (to 7.5 × 1cm), with a rounded base, an acuminate apex, and serrate margins, 3-nerved at the base, and with 5 or 6 secondary veins on either side of the midrib. The midrib and secondary veins possess a scattering of hairs.

The calyx lobes are oblong-lanceolate, with acute or subacuminate apices, and are 5 mm long. The asymmetrically broadly obovate petals are 6-7 mm long, with truncate or slightly retuse apices. The ligulate staminodes are 6 mm long. The stamens are appreciably shorter than the staminodes, and the middle stamen of each group of three appreciably shorter than the flanking stamens. The ovaries have 5 locules.

The pollen grains are oblately spheroidal, with a polar diameter of about 46μ and an equatorial diameter of about 52μ. Their spines are about 6μ long, with a basal diameter of about 4.5μ. [8]

There are no known synonyms of Paradombeya burmanica.

Paradombeya sinensis Dunn.
Chinese ping dang shu

Paradombeya sinensis is found Yunnan and south and southwest Sichuan in China, where it is found in open scrub on grassy slopes, at a height of 300 to 1500 m.

It is a small tree or shrub, growing up to 5m. The slender twigs have a sparse covering of stellate hairs. The foliage is alternate, stipulate, and either sessile or shortly petiolate (petioles to 5mm in length). The stipule is filiform, and is lost early in leaf development. The leaf blades are ovate-lancoleate to elliptic-oblanceolate, of dimensions 5-12.5×1.5-5 cm, 3-nerved at the base, with around 10 lateral veins on either side of the midrib, with a rounded or shallowly cordate base, a long acuminate apex, and serrulate margin. The blade has a membranous texture. The upper side has a sparse covering of stellate hairs; the lower side is glabrous or nearly so.

The flowers are borne in fasciculate cymose clusters in the leaf axils. They have slender 1-1.5 cm long pedicels, and a 3-lobed caducuous epicalyx with lanceolate lobes. The calyx lobes are short (about 4 mm long) and ovate-lanceolate. The petals are yellow and broadly obovate, with truncate apices, and differ in size among themselves, but are around 5 mm long. There are 15 stamens, arranged in five groups of three, the groups alternating with 5 ligulate staminodes. The staminodes are slightly shorter than the petals. The filaments are fused at their bases, forming a short tube. The anthers are ovate to elliptic. The style is hairless and awl-shaped.

The fruit is a somewhat subglobose capsule, with a diameter of about 2.5mm, divided into two locules, each containing a single seed. Its surface is coated with stellate hairs. The locules are easily separated. The seeds are dark brown, oblong-ovoid in shape, and about 1.5 mm long. [1, 5]

The diploid chromosome count for Paradombeya sinensis is 20 [5]

There are no known synonyms of Paradombeya sinensis..

Images

References

  1. Wu, Z. Y., P. H. Raven & D. Y. Hong, eds, Flora of China 12: 330 (2007)
  2. Kubitzki & Bayer, Malvaceae, in Kubitzki & Bayer, Fam. Gen. Vasc. Plants V: 270 (2003)
  3. Checklist of the Plants of Myanmar (2003)
  4. Stapf, Paradombeya burmanica and Paradombeya sinensis, Icones Plantarum 28(2): t. 2743 (1902)
  5. Tang, On the systematic position of Paradombeya Stapf , Acta Phytotax. Sin. 31(4): 297-308 (1993)
  6. Biodiversity of the Hengduan Mountains
  7. Biodiversity Inventory of the Gaoligong Shan
  8. G. Erdtmann, Pollen Morphology and Plant Taxonomy 418 (1952)

Malvaceae Info (Home)
Partial Synonymy of Asian Dombeyoid Genera