Xenophyllum acerosum (Cuatrec.) V.A.Funk, Novon 7(3): 238. 1997.

Calvo, Joel & Moreira-Munoz, Andres, 2020, Taxonomic revision of the Andean genus Xenophyllum (Compositae, Senecioneae), PhytoKeys 158, pp. 1-106 : 1

1. Xenophyllum acerosum (Cuatrec.) V.A.Funk, Novon 7(3): 238. 1997.

Werneria acerosa Cuatrec., Brittonia 8: 45. 1954. Type. Ecuador. Azuay: “Oriente” border, eastern Cordillera, between Oña and the río Yacuambi, 3050-3415 m, 10/19 Sep 1945, F. Prieto 280 (holotype: F-1402673!; isotypes: G-00305681 (digital image!), GH s.n.!, K-000527742 (digital image!), MO-1652045!, NY s.n.!, P-02088566 (digital image!), S-R-6520 (digital image!), UC-986455!, US-00037296!, VEN-34483 (digital image!)).

Description.

Suffruticose plant, forming distant, rather solitary, erect stems. Rhizomes 6-10 × 0.2-0.3 cm, horizontal to oblique, glabrous. Stems 12-20 cm tall, usually simple, sometimes branched at the upper part, covered with adpressed, arachnoid trichomes, with leaves restricted to the upper part. Leaves imbricate, extending into a sheath-like base that bears arachnoid trichomes; leaf laminas 4.6-5 × ca. 0.9 mm, linear-acicular, aristate at the apex (arista up to 1 mm long, purplish), entire, terete in cross section, glabrous, unconspicuously nerved on both faces, somewhat fleshy, drying coriaceous, matte, papillose. Capitula radiate, erect, sessile, partially enclosed among the leaves. Involucres ca. 8.6 × 7.3 mm, cupuliform; involucral bracts ca. 13, 5.2-5.5 × 1.1-1.6 mm, rather acute at the apex, dark-purplish. Ray florets ca. 13; corollas ca. 12 × 2.3-2.5 mm, 4 to 5-veined, subentire to 3-toothed at the apex, conspicuously surpassing the involucre, white, purplish beneath. Disc florets ca. 50; corollas 3.8-4.2 mm long, pale yellow to creamy; style branches truncate with a crown of sweeping trichomes, yellowish. Achenes cylindrical, with scattered arachnoid trichomes (immature); pappus 3.1-3.3 mm long, barbellate, whitish. Chromosome number unknown. Fig. 5 .

Distribution and habitat.

Endemic to Ecuador (Azuay, Zamora-Chinchipe [expected]). It grows in marshy places of the paramo ecoregion, between elevations of 3050-3070 m (Fig. 6 ).

Thus far, X. acerosum is only known from the type locality in the paramo of Yacumbi, which is located above Saraguro on the border between the Ecuadorian provinces of Azuay and Zamora-Chinchipe.

Phenology.

Collected in flower in September and November.

Etymology.

The adjective acerosus -a -um means needle-shaped, and it refers to the leaf shape of this species.

Notes.

Xenophyllum acerosum is unique in the genus in its distant, rather solitary, erect stems arising from long rhizomes and by its linear-acicular, aristate leaves. The stems only bear leaves in the upper part.

Additional specimen examined.

Ecuador. Azuay: Cordillera Cordoncillo, along road from Babes (ca. 2 km E of Urdaneta) towards 28 de Mayo, 3°34'S, 79°6'W, 10 Nov 2018, P. Sklenář 15820 (PRC n.v., QCA).

Figures

Figure 5. Xenophyllum acerosum A habit B stem apical part and capitulum C detail of leaf surface D adaxial leaf surface E ray corolla and style F disc corolla and stamens (vertically sectioned, style removed) G disc corolla and style branches H style I immature achene with pappus. All details drawn from Prieto 280 (US). Illustration by Alice Tangerini.

Figure 6. Distribution map of Xenophyllum acerosum (left hand) and X. humile (right hand).