Aspidostemon occultum, Werff, 2006

Werff, Henk Van Der, 2006, A revision of the Malagasy endemic genus Aspidostemon Rohwer & Richter (Lauraceae), Adansonia (3) 28 (1), pp. 7-44 : 36-37

21. Aspidostemon occultum

Van der Werff, sp. nov. ( Figs 13B ; 14A )

A congeneris foliis papyraceis, acuminatis, floribus depresse globosis differt.

TYPUS. — Madagascar. À la base du Mur de l’Ankarana , [12°54’S, 49°08’E], 16-28. I.1969, fl., fr., Service Forestier 28709 (holo-, P; iso-, MO, TEF).

DESCRIPTION

Tree, to 25 m. Twigs terete, glabrous; terminal buds glabrous. Leaves opposite, 9-13 × 2.5-3.5 cm, papyraceous, glabrous, elliptic, the base acute, apex acuminate, the acumen 1 cm long, often rolled into a cylinder, the margin flat, reticulation immersed on both surfaces, lateral veins scarcely visible; petioles 7-10 mm long, shallowly canaliculate. Inflorescences to 3 cm long, glabrous, paniculate; pedicels 1-2 mm long. Flowers depressed globose, glabrous, wider than long, 2-2.5 mm in diam., tepals short, wider than long, erect; stamens 6, the outer three opening before the inner three and thus younger flowers seemingly with 3 stamens, glabrous, locelli apical; staminodia III with large, peltate apex, free or fused, upper rim of the receptacle and base of the staminodia III pubescent; staminodia IV not seen; pistil slender, glabrous, inside of the receptacle glabrous. Fruits 2.2 × 1.5 cm, ellipsoid, smooth, crowned with floral remnants.

REMARKS

Aspidostemon occultum is best recognized by its thin, acuminate leaves, depressed globose flowers with large staminodia III. It is only known from the type collection made in the NW part of Madagascar ( Fig. 12 ). The interpretation of the number of stamens requires some explanation. In most species of Aspidostemon the number of stamens, 3 or 6, is easy to determine. Sometimes in a species with 3 stamens the staminodial second whorl may have rudimentary locelli, which are visible as light colored patches. These rudimentary locelli do not open and can thus be recognized as rudimentary. In Aspidostemon occultum however, most flowers have 3 stamens, but there are also some flowers with six stamens, all with opened locelli. These flowers can be considered as fully mature and the flowers with 3 stamens as not yet fully mature (the tepals cover the stamens of whorl II in these flowers) or the flowers with 6 stamens can be regarded as anomalous and ignored. I accept the first explanation: mature flowers have 6 stamens, of which the outer 3 open first and the inner 3 later. The same phenomenon has been observed in A. andohahelense and A. manongarivense : some flowers have 3 stamens, others 6. No vernacular name has been recorded.

ALTITUDINAL DISTRIBUTION

50-100 m.

PHENOLOGY

Flowers and fruits: January.

Figures

FIG. 13. — Scanning electron microscope images of Aspidostemon Rohwer & Richter: A, A. microphyllum Van der Werff; B, A. occultum Van der Werff; C, A. parvifolium (Scott-Elliott) Van der Werff; D, A. trichandra Van der Werff. A, Schatz & Carlson 2925, MO; B, Service Forestier 28709, MO; C, McPherson 14362, MO; D, Ranirison 528, MO. Scale bars: 0.5 mm.

FIG. 14. — Species of Aspidostemon Rohwer & Richter: A, A. occultum Van der Werff; B, A. parvifolium (Scott-Elliott) Van der Werff; C, A. percoriaceum (Kosterm.) Rohwer; D, A. perrieri (Danguy) Rohwer. A, Service Forestier 28709, MO; B, McPherson 14362, MO; C, Service Forestier 1983, MO; D, Thouvenot 115, MO.

FIG. 12. — Distribution of Aspidostemon Rohwer & Richter in Madagascar: Ϙ, A. macrophyllum Van der Werff; ■, A. manongarivense Van der Werff; Ϙ, A. masoalense Van der Werff; ▲, A. occultum Van der Werff.