Amorphophallus sagittarius: The Smallest Aroid of Java Hidden in West Java’s Hills
Tucked away in the secondary forests of a single hillside in West Java, Amorphophallus sagittarius Steenis holds a remarkable distinction: it is the smallest Amorphophallus species known from Java. Steenis described it formally in 1953 in Acta Botanica Neerlandica. Despite its diminutive size, it displays all the morphological complexity typical of the genus — from a uniquely marbled, bicolored petiole to a strongly zygomorphic stigma unlike that of most relatives. Endemic to the Situ Gunung area of Sukabumi, West Java, this species represents both a botanical curiosity and a locally endemic conservation priority. For botanists specializing in Javan flora, A. sagittarius is an unmistakable miniature gem.
Taxonomic Identity of Amorphophallus sagittarius
Amorphophallus sagittarius belongs to the family Araceae. Steenis described it in Acta Bot. Neerl. 2, 3 (1953): 302. No synonyms are currently recognized for this species.
Morphological Description
Tuber and Leaf
The tuber of Amorphophallus sagittarius is subglobose, yellowish-brown, approximately 6 cm in diameter and 4–5 cm tall, weighing up to about 120 g. It produces no offsets. Instead, it gradually disintegrates to form new tubers. Accessory buds appear in slightly raised groups. The plant bears a single solitary leaf. The petiole is smooth, slender, and turgid, 30–40 cm long and approximately 1 cm in diameter at the base. Its ground color varies from dark green near the base to mid-green above. The surface is marbled with slightly paler, bright green spots that carry a bicolored margin — very pale whitish-green and blackish-green — almost entirely covering the surface toward the top of the petiole.
The lamina is 60–80 cm in diameter, with unwinged rachises. Leaflets are elongate-elliptic, acuminate, 6–23 cm long and 2.5–9 cm wide. Their upper surface is moderately glossy green, and the lower surface is greyish-green. Venation is impressed on the upper side.
Inflorescence and Peduncle
The inflorescence of Amorphophallus sagittarius is solitary and short to medium-peduncled. The peduncle reaches 12–21 cm in length and 0.5–0.8 cm in diameter. It matches the petiole in color, or carries an extra brownish hue.
Spathe
The spathe is erect, 13–16 cm long and 9–10 cm in diameter. It is ovate to elongate-ovate and obtuse to acute at the apex. It is more or less twisted near the top. The outer base surface is pale brown with large or small, pale green or white, isolated or partly confluent spots. The outer limb surface is largely maroon and glossy. The inner limb surface is also maroon and glossy. The inner base surface carries many small warts.
Spadix and Floral Zones
The spadix of Amorphophallus sagittarius subequals or equals the spathe in length, measuring 13–15.5 cm. The female zone is cylindric, 1.3–2 cm long and 0.8–1 cm in diameter. Its flowers are mostly congested or slightly distant. The male zone is subcylindric and slightly obconic, approximately 3.5 cm long and 0.8–1 cm in diameter. Flowers in the male zone are congested. The appendix is elongate and acute, 7–9.5 cm long and 1–1.4 cm in diameter near the base. Its surface is off-white and minutely or more distinctly verrucate.
Female Flowers
Each ovary is globose to subglobose, 2–4 mm in diameter and 1.5–2.5 mm tall. It is circular in cross-section and unilocular, with one basal ovule. The ovary is bright pale green, sometimes maroon near the style insertion. The style is very short to near-absent, measuring subzero to 0.5 mm long and approximately 1 mm in diameter, and maroon. The stigma is 1–1.5 mm in diameter. It is strongly zygomorphic, flat, disciform, or with a variously folded margin. It often results in 3 lobes — 2 basiscopic and 1 large acute acroscopic — separated by several shallow grooves. The surface is off-white and densely minutely verrucate.
Male Flowers
Each male flower carries 3–4 stamens. Stamens are subtruncate and 2 mm long. Filaments are 1 mm long and basally connate. Anthers are polygonal in cross-section, 1 mm long and 1–2 mm in diameter. They are pale yellowish or pale purplish-violet. Pores are apical.
Distribution of Amorphophallus sagittarius
Amorphophallus sagittarius is locally endemic to Situ Gunung, Sukabumi, West Java, Indonesia. It occurs nowhere else in the world. This extremely restricted distribution makes it one of the most narrowly distributed plants in the entire Javan flora.
For verified occurrence data and distribution records, refer to GBIF – Amorphophallus sagittarius and the Plants of the World Online (POWO) – Kew.
Habitat
This species grows in secondary forests on slopes. Its hillside habitat in the Situ Gunung area of Sukabumi places it in a relatively humid, forested environment. Conservation of these secondary slopes is therefore essential to the continued survival of the species.
Taxonomic Notes
Amorphophallus sagittarius is the smallest species in the genus known from Java. Its nearest morphological relative is A. variabilis, which shares a similar general habit. Nevertheless, two consistent characters differentiate them clearly. First, A. sagittarius carries a short peduncle of up to 21 cm, versus up to 120 cm in A. variabilis. Second, the spadix of A. sagittarius subequals the spathe in length, while in A. variabilis the spadix is mostly about twice the spathe length. These two quantitative differences are reliable and immediately apparent when comparing flowering specimens of the two species.
Photo Reference
References
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- Steenis, C.G.G.J. van (1953). Amorphophallus sagittarius Steenis. In: Acta Bot. Neerl. 2, 3: 302.
- Yuzammi (2009). The genus Amorphophallus Blume ex Decaisne (Araceae – Thomsonieae) in Java. Reinwardtia 13: 1–12.
- Kew Science. Amorphophallus sagittarius Steenis – Plants of the World Online. Available at: https://powo.science.kew.org/taxon/84434-1
- GBIF Secretariat. Amorphophallus sagittarius occurrence data. Global Biodiversity Information Facility. Available at: https://www.gbif.org/species/2871473
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