The Hildegardia Page

Malvaceae Info (Home)
Hildegardia Gallery
Synonymy of Hildegardia

Introduction

Hildegardia is a genus of 12 species of malvaceous trees, placed in subfamily Sterculioideae/tribe Sterculieae. It has a pantropical distribution (West Africa, East Africa, Madagascar, southern India, Philippines, Indonesia, northern Australia and Cuba). The genus was introduced in 1832 [1] and revised in 1954 [a]. Additional species have be described in or tranferred to the genus in subsequent years. The type species is Hildegardia populifolia [2] (Roxb.) Schott. & Endl.

[Note: Kubitzki and Bayer [3] and Zaborsky [4] recognise an additional species, Hildegardia major, from China. I follow the Flora of China [5] in placing this species in Firmiana.]

The genus is the type of Reichenbach's [b] (currently unrecognised) suprageneric taxon Hildegardieae.

The genus is distinguished from other genera of Sterculieae by the combination of the traits of indehiscent (not dehiscent) and thin, membraneous or papery (not thick, leathery or woody) fruits. Like the other genera of the tribe its flowers lack petals, and also lack an epicalyx, but possess an androgynophore.

The leaves are thin, broadly ovate, unlobed or slightly lobed, cordate at the base, palmately nerved, with entire margins, and sometimes with domatia. The inflorescence is composed of raceme like panicles at the end of the shoots. The flowers are polygamous, some being hermaphrodite, others unisexual. The calyx is tubular, 4- or 5-lobed, usually petaloid and reddish in colour, and persistent in fruit. The stamens number twice or thrice the number of sepals, and are united in a longish androgynophore, at the end of which the anthers are sessile, and clustered around the carpels. The anthers are 2-locular. The carpels number 5, borne on a short stalk, and soon separate from each other. They are uniovulate or biovulate. In fruit they are free, long-stalked, and indehiscent, with a membranous and reticulate coat.[2, 3]

The African and Malagasy species appear to form a natural group in which the calyx is tubular, and only shortly divided at the apex, and which flower when the plant is bare of leaves [6]. The former constrasts with the deeply divided calyx and reflexed sepals of Hildegardia australiensis and Hildegardia populifolia, while the flowers of Hildegardia cubensis are intermediate. A study of DNA sequences from Sterculioideae [c] found that Hildegardia and Firmiana did not form mutually distinct clades, implying that a revision of these two genera is necessary.

Hildegardia millenari, mention of which can be found on the WWW, is fictional. Hildegardia is also a genus of grasshoppers.

Hildegardia ankaranensis (Arènes) Kosterm.

Hildegardia ankaranesis is in found deciduous forest on the hilla and plateaux of the northern tip of Madagascar, most frequently in Ankarana reserve, from which the specific epithet is presumably taken [7].

It is a large tree. The trunk can attain a diameter of 1m or more [7].

The leaves are long petiolate, broadly ovate or suborbicular to 17 × 15 cm, palmately 7–9-nervate, cordate at the base and weakly 3-lobed. The lobes are variably acuminate, in some leaves only the central lobe being so. The flowers are tubular and orange-red in colour, the individual sepals being fused almost to the apex. The fruit is composed of 5 follicles. The 2-seeded follicles are relatively large (9 × 6½cm), more or less flattened, with a thick coriaceous pericarp. Their indumentum is velutinous. It is brown or ferriginuous on the outside, and fawn-coloured, and composed of stellate hairs on the inside [7].

Sterculia ankaranensis Arnes is a synonym of Hildegardia ankaranensis.

Hildegardia australiensis G.J.Leach & Cheek

A recently (1991) described deciduous species, related to Hildegardia sundaica, from the Western Arnhem Land plateau in Australia's Northern Territory.

It is a deciduous tree growing to 7-10m in height. The bark of the trunk is mostly smooth, with fine lengthwise fissures, and light grey in colour. Young wood is covered with white, flaky, waxy coating. The blade of the leaf is simple and palmately 7-nerved [8].

In common with several other species of this genus, and also with the Australian endemic genus Brachychiton, the flowers are borne during the leafless period.The species is apparently dioecious. Female flowers were not available when the species was described, and no subsequent description has come to hand. The calyx of the male flowers is composed of 4 or 5 reflexed strap-like orange to red sepals, divided almost to the base, where they are fused into a cup like structure. The individual sepals are 9-11mm long and 2mm wide. Their lower surface is covered with peltate scales. A cluster of 8-10 yellow anthers is borne at the summit of a dull yellow stalk, described by Leach and Cheek as an androphore. This is slender at its base and apex, and swollen in the middle. These male flowers are highly scented. [8, 9]

The fruit is composed of 4 or 5 inflated and winged fruitlets. Each fruitlet contains 1 or 2 spherical seeds. [8]

Hildegardia barteri (Mast.) Kosterm.