[Botany • 2026] Impatiens yakandawalarum (Balsaminaceae) • A New ecalcarate Species of Impatiens from the lowland wet zone of Sri Lanka

 

 Impatiens yakandawalarum  Gopallawa, Hapuarachchi & Jayathissa, 

in Gopallawa, Hapuarachchi, Jayathissa, Gunarathna et Karunarathna, 2026. 

DOI: doi.org/10.4038/cjs.v55i4.10118  

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Abstract

Impatiens yakandawalarum Gopallawa, Hapuarachchi & Jayathissa, sp. nov., a new ecalcarate species from the lowland wet zone of Sri Lanka, is described and illustrated based on morphological evidence. The species was discovered on a wet rocky slope at Manna Kathi Ella, Kitulgala, Kegalle District, and represents the first Sri Lankan Impatiens characterized by a consistently ecalcarate lower sepal across the examined population and material. It is distinguished by a completely ecalcarate navicular lower sepal, a fleshy, globose to subglobose subterranean storage organ, and glabrous leaves. The flowers superficially resemble those of Impatiens thwaitesii Hook.f. ex Grey-Wilson, while the habit shows similarities to Impatiens janthina Thwaites. A description, illustrations, comparisons, and a preliminary conservation assessment are provided.

Keywords: ecalcarate, endemic species, Kitulgala, lithophyte, fleshy subterranean storage organ

Floral and vegetative morphology of Impatiens yakandawalarum sp. nov.
  A. Flower, frontal view. B. Dissected floral parts showing dorsal petal, lateral petals, lateral sepals. C. Androecium. D. Fruiting capsule. E. Dehisced capsule and seeds. F. Cross section of seed capsule. G. Lower sepal, inner and lateral views. H. Flower, lateral view. I. Flower, rear view. J. Floral bracts. K. Flower buds, lateral and dorsal views. L. Leaf variation, adaxial and abaxial surfaces. M. Leaf margin. N. Habit. O. Basal stem and fibrous roots. P. Longitudinal section of fleshy, globose to subglobose subterranean storage organ. Q. Fleshy, globose to subglobose subterranean storage organ with fibrous roots. Scale bars as indicated

Impatiens yakandawalarum Gopallawa, Hapuarachchi & Jayathissa, sp. nov.

Diagnosis: Impatiens yakandawalarum differs from I. thwaitesii in possessing a globose to subglobose subterranean storage organ (vs absent), glabrous leaves (vs pubescent adaxially), terminal 2 – 3-flowered, umbel-like racemes (vs 6- to many-flowered subumbellate racemes), and a completely ecalcarate navicular lower sepal with a linear series of purplish-pink internal spots (vs a spurred lower sepal without such a linear series). It differs from I. janthina in its branched, 4 – 6 mm thick stem, terminal 2 – 3-flowered racemes with peduncles 5 – 16 cm long, completely ecalcarate lower sepal, and elongate-fusiform capsules.

Etymology: The specific epithet honours Professor Deepthi Yakandawala and Professor Kapila Yakandawala for their contributions to plant taxonomy, systematics, forestry, conservation and botanical research in Sri Lanka. As the epithet commemorates two people sharing the surname Yakandawala, yakandawalarum is formed as a genitive plural by adding -rum to a personal name ending in -a, in accordance with Art. 60.8 of the International Code of Nomenclature for algae, fungi, and plants (Turland et al., 2025). 

Proposed common names E. Kitulgala Balsam,
S. කිතුල්ගල කූඩලු

Bhathiya Gopallawa, S. I. Hapuarachchi, Chathura Jayathissa, S. S. Gunarathna and Peshala Pasan Karunarathna. 2026. A New ecalcarate Species of Impatiens (Balsaminaceae) from the lowland wet zone of Sri Lanka. Ceylon Journal of Science. 55(4); 1424-1433. DOI: doi.org/10.4038/cjs.v55i4.10118 [Sep 30, 2026] 

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