XEROPHILUM Pino, Alcalá & Marquiegui, 2021

Type : Pino, Alcalá & Marquiegui 3251, Peru, dept. Huancavelica, prov. Castrovirreyna, distr. Arma, 1963 m, Jan 19, 2021.

Etymology : Referring to the dry places where S. xerophilum is occurring.

Distribution : Found in only few scattered populations in the dept. Huancavelica, close to the coastal desert of Ica, at lower elevations than the rest of the Peruvian Sedum species (1900 – 2400 m), and always together with many species of Cacti.

Description :

A succulent glabrous herb, caespitose, forming loose mats to 10–12 cm diam. 

Roots fibrous, 0.2–0.3 mm diam. 

Basal stem 3–7 cm long, 2–2.2 mm diam., gradually tapering to 1.6–1.8 mm, decumbent, then branching alternately every 1–3 cm, light green with brownish red stripes towards apex, light greenish grey in old plants. 

Branches 4–12, erect to slightly decumbent, frequently bended, vegetative branches 8-9 mm diam., 5–7 cm long, covered in leaves, reproductive branches 4-5 mm diam., up to 15 cm long in blossom.

Leaves succulent, sessile, spirally attached to stem, in vegetative branches every 1.5–2 mm, in reproductive branches less densely towards apex (up to 3–4 mm apart),  broadly ovate on vegetative stems, both sides convex, 3.2–4.5 mm long,  2.5–4 mm wide (narrower near inflorescence), 2–2.2 mm thick, near inflorescence incurved and concave, base attached in 45º angle to stem, apex obtuse or rounded, olive green with a slight blush towards apex, margins blunt, base hyaline, light green. 

Inflorescence a terminal cyme (dichasium) with 2 cincinnoid branches and a flower at bifurcation. Each branch 1.8–1.6 mm diam. at base, gradually tapering to 1mm, 7–8 mm long, light green. 

Flowers 3–5 per cincinnus, sessile, appearing in habitat from January to February. Flower buds ovoid, 5–7 mm long, 3.5–5 mm diam., olive green. Bracteoles one at the base of each flower, ovate, 3–5 mm long, 2–3.5 mm wide, subacute, upper side flat, lower side convex, olive green. Sepals narrowly ovate, 3–3.5 mm long, 2–2.2 mm wide, erect, outer side olive green. Petals oblong, acute-deltoid at tip, erect, very slightly recurving, 4–4.5 mm long, 1.5–2 mm wide, both sides greenish white to yellowish, outside brownish at keel of distal third. Flower diam. 4–4.8 mm. Stamens 10, the 5 epipetalous 2.2–2.5 mm long, the antesepalous 3–3.2 mm long, filaments white, 0.2–0.3 mm diam. Anthers globose, yellow, 0.3–0.4 mm diam. 

First described in CSJ US 93(4) : 298-300. 2021.

Note :

S. xerophilum is similar to S. berillonanum, the main difference being the flowers : the petals of the latter are longer and narrower, pure white and spreading at the middle. The geographically closest Sedum species is S. incarum, however the latter is much taller and has twice as long leaves. While flowers are rather similar, the structure of the inflorescence is remarkably different : S. incarum has a much more complex inflorescence.