Pseuderanthemum is a genus of flowering plants in the family Acanthaceae (order Lamiales), comprising roughly 130–168 accepted species distributed across the tropics of Africa, Asia, the Pacific Islands, and the Americas. The genus was described by the German botanist Ludwig Radlkofer and published in 1883–1884 in Sitzungsberichte der Mathematisch-Physikalischen Classe der Königlich Bayerischen Akademie der Wissenschaften.
Members of the genus are herbs or shrubs characterised by the presence of cystoliths (calcium carbonate deposits visible in the leaf tissue). Leaves are sessile or petiolate with entire or nearly entire margins. The flowers are borne in axillary or terminal thyrses, racemes, or spikes, with bracts and bracteoles shorter than the calyx. The calyx is deeply five-lobed; the corolla is salverform — narrow-tubed with a spreading five-lobed or weakly two-lipped limb whose lobes are ascending-cochlear in bud. The functional stamens number only two (sometimes with two additional staminodes), and the anthers are two-thecous with parallel, equal thecae. The fruit is a clavate capsule with a long solid stalk, containing four seeds; each seed is lenticular and smooth or ornamented, without trichomes.
The genus has a pantropical distribution and is well represented in South and Southeast Asia, the Pacific Islands, tropical Africa, and the Neotropics. About 50 species are recognised in the Flora of China treatment, seven of them occurring in China (two endemic). Several species are cultivated as ornamental foliage or flowering plants in tropical and subtropical gardens, with P. carruthersii and its cultivars among the most widely grown.
Etymology
The genus name Pseuderanthemum derives from the Greek pseudo- (false) combined with Eranthemum, a related genus in Acanthaceae, indicating its morphological resemblance to Eranthemum while being distinct. The name was coined by Ludwig Radlkofer (abbreviated "Radlk.") in 1883.
Distribution
Pseuderanthemum has a pantropical distribution, occurring across tropical Africa (including Angola, Benin, Burundi, Cameroon, and the Central African Republic), South and Southeast Asia (Andaman Islands, Assam, Bangladesh, Borneo, Cambodia), the Pacific Islands (Bismarck Archipelago, Caroline Islands), and the Neotropics (Belize, Bolivia, Brazil). In China, about seven species are recorded, two of them endemic.
Taxonomy Notes
The genus Pseuderanthemum Radlk. was described in 1883 and belongs to the tribe Justicieae within Acanthaceae. It is closely allied to Eranthemum, from which it is distinguished by a combination of floral and fruit characters including the clavate capsule with a long solid stalk and the cochlear bud arrangement of the corolla lobes. Plants of the World Online accepts approximately 130 species as of 2022; the GBIF backbone recognises ~168 descendants. Some species are heterostylous.
