Psidium schenckianum Kiaerskou (1893: 34).

Type:— BRAZIL, “Garanhuus [Garanhuns] Prov. Pernambuco,” J.H.R. Schenck 4239 (C10015967!, lectotype here designated; isolectotypes C10015968; C10015968!)

= Psidium oncocalyx Burret (1941: 56). Type:— BRAZIL, Bahia, auf Bergen bei Maracás, 1–2 m hoher Strauch mit weiβen Blüten (blühend Sept. 1906)” E. Ule 6975 (B†, presumed destroyed; HBG-527373, lectotype here designated, image!), syn. nov.

Treelet or shrub, 0.8–4m tall; new growth puberulous, hairs brownish. Old branches cylindrical, grey, finely striate, sometimes peeling in thin, long fibers; young branches strongly flattened at nodes. Leaves short-petiolate to subsessile; petioles 1–2 mm long; blades ovate or elliptic-oblong, 1.5–2.5 × 0.7–1.5 cm, apex rounded or acute, base rounded or obtuse, chartaceous; margins revolute, sometimes folded longitudinally in pressed material and hiding the abaxial surface; adaxial surface glabrous to sparsely pubescent, venation brochidodromous, lateral veins (2–) 4–6 pairs, barely perceptible in older leaves, ascending at 50°–60° and fading out, old leaves essentially avenious except for the midvein; abaxial surfaces sparsely pubescent, more densely so along midvein and leaf margin, becoming glabrous with age; midvein slightly sulcate or plane above and prominent below. Flowers solitary, pedicels 8–17 mm long; bracts deltoid or linear, c. 2 × 2 mm long; bracteoles linear, c. 3 mm long; floral buds widely pyriform, 3–6 mm long, calyx open, 5-merous, sepals with buttressshaped appendices caused by the coalescence of the tips, internally sericeous; petals 5, sometimes pink in bud, white in the open flower, obovate, 3–4 mm long, externally sericeous, ciliate; staminal disk flat, pentagonal, thin, not tearing at anthesis; stamens 160–203 (fide Stadnik et al. 2018); ovary 3–locular, ovules uniseriate on the placenta, 5–10 ovules per locule; style c. 4 mm, stigma punctiform. Fruit yellowish and rounded when mature, 5–7 × 6–6.5 mm, glabrous, crowned by the torn, explanate or somewhat revolute calyx remnants, the pulp scarce; seeds 3 to 7, tightly clustered into a ball, tan, angulatelenticular, 3–4.5 × c. 4 mm, the opercular plug columellar, pulpy.

Vernacular names:— Araçá (Sergipe; Serviço Florestal Brasileiro 2017); araçá-de-moça (Bahia; cited on specimen Gomes 79); cambuí (Bahia; cited on specimen Silva et al. 2236); cambuí-de-acu (Bahia; cited on specimen Gomes et al. 334); boquinha-doce (Bahia; cited on specimen Mortari 13); guabiraba (Bahia; cited on specimen Ribeiro et al. 123); murta (Bahia; cited on specimen Cardoso 500); pirico (Bahia; cited on specimen Cardoso & Santos 218); pirim (Pernambuco; Jacob et al. 2020).

Taxonomic notes:— Burret (1941) compared P. oncocalyx to P. glaziovianum Kiaeskou (1893: 33), but he seems to have missed the great similarity between P. oncocalyx and P. schenckianum. Psidium schenkianum, the oldest name, has “Garanhuus [Garanhuns] Prov. Pernambuco,” as its type locality, and two specimens were indicated as types: Schenck 4172 and 4239 (syntypes). To diminish taxonomic and nomenclatural ambiguity and aid identification, a lectotype for Psidium schenckianum was herein elected and designated.

Psidium oncocalyx Burret (1941: 34) was described based on a specimen collected in Maracás, Bahia, by Ernst Ule (number 6975) in 1906. The species was characterized as a shrub 1–2 m, with solitary flowers, a hook-shaped, 5-merous calyx, leaves elliptic-oblong, with revolute margins. It is accepted (Ulloa et al. 2012, POWO 2023) but up until now was known only from the description in the protologue. Ule numbers 6972 and 6973 (not Myrtaceae) are recorded in the Berlin Negatives Collection (https://collections-botany.fieldmuseum.org/project/6454) but number 6975 is not. Since P. oncocalyx was described in 1941 by Max Burret, who worked at the Botanischer Garten und Botanisches Museums Berlin-Dahlem (B), we believe it is highly likely that the holotype specimen was destroyed. Many thousands of collections at B were destroyed during the World War II hostilities (Merrill, 1943). When Francis MacBride, based at B, was visiting major European Herbaria between 1929–1940 to photograph types for the Field Museum of Natural History (see Grimé & Plowman, 1987 for a short history), he did not have access to the B Myrtaceae because Burret kept all the Myrtaceae in his office (Rogers McVaugh, pers. comm.). Therefore, the Field Museum Negative collection contains no Myrtaceae from Berlin (https:// collections-botany.fieldmuseum.org/project/6454). This is unfortunate because the major 19 th century Myrtaceae specialist, Otto Carl Berg, who described c. 1000 species of New World Myrtaceae (McVaugh, 1968), was based in Berlin.

Psidium schenckianum is a member of Psidium sect. Mitranthes Tuler & Proença (Proença et al. 2022). It is sometimes confused with Psidium ganevii Landrum & Funch (2008: 75) that it greatly resembles in the size and shape of the leaves, and in the small, solitary flowers. Psidium ganevii, however, tends to have shiny upper leaf surfaces and thick, loose calyx lobes that do not closely clasp the flower bud and, more importantly, lacks the conspicuous buttresses of P. schenckianum (Fig. 1c).

Geographic distribution:— Psidium schenckianum Kiaerskou is endemic to Brazil. It occurs in Alagoas, Bahia, Pernambuco, Sergipe and northern Minas Gerais (Fig. 2).

Ecological notes:— Psidium schenckianum occurs mainly in the Caatinga and its interfaces with Cerrado and other neighbouring phytogeographic provinces. The cited habitats are: Atlantic rainforest, campos rupestres, capão, carrasco, dense ombrophilous forest, seasonal deciduous forest and riparian forest. It occurs between c. 120–1110 m alt., and collectors frequently cite sandy soil with rocks or boulders. Floral buds were recorded in all months of the year except June and July, with December as the month of highest probability. Flowers were found in all months of the year except June and August, with the month with the highest probability being January. Fruits (at any stage of maturity, from very young to mature) were recorded in all months of the year, with highest probability in March. Mature fruits were recorded between January and May, with the highest probability of occurrence in April.

Ethnobotanical notes:— Psidium schenckianum has been used for centuries in the region of the Caatinga, its edible fruits consumed in natura or made into a liqueur or used medicinally for throat infections (Bezerra et al. 2022, Nascimento et al. 2011, Cruz et al. 2013; Nascimento et al. 2013, Cruz et al. 2014). The liqueur is made by infusing the mature fruits for several months in bottles with handmade or industrial sugar cane rum (cachaça) to develop the flavor (Fig. 1e). However, the use of this fruit has become increasingly restricted to traditional populations, and a reduction in the size of the P. schenckianum populations is probably in motion due to the fragmentation of the Caatinga (Jacob et al. 2020; Liporacci et al. 2017).