Euphorbia humifusa Willdenow, Enum. Pl. Suppl.

Mugnai, Michele, Lazzaro, Lorenzo, Nuzzo, Luca Di, Foggi, Bruno, Viciani, Daniele & Ferretti, Giulio, 2021, Synopsis of Euphorbia section Anisophyllum (Euphorbiaceae) in Italy, with an insight on variation of distribution over time in Tuscany, Phytotaxa 485 (1), pp. 1-65 : 21-22

6. Euphorbia humifusa Willdenow, Enum. Pl. Suppl. : 27. 1813.

Type (lectotype, here designated):—[s.l.]. humifusa s.d., C. L. Willdenow s.n. (B-W9283-01.0 image!), https://plants. jstor.org/stable/viewer/10.5555/al.ap.specimen.b%20-w%2009283%20-01%200

≡ Chamaesyce humifusa (Willd.) Prokhanov (1927: 195)

≡ Anisophyllum humifusum (Willd.) Klotzsch & Garcke in Klotzsch (1860: 21)

≡ Tithymalus humifusus (Willd.) Bubani (1897: 116)

= Euphorbia polygonisperma Grenier & Godron (1855: 75) . Type:—Not found.

Description:—Herbs, annual, with fibrous roots. Stems prostrate to ascending, 20–30 cm, often red or pinkish red, glabrous or pilose. Leaves opposite; stipules distinct, membranous, deeply divided into filiform lobes, 1.5 mm, caducous; petiole 1–2 mm; blade obliquely oblong-oblanceolate, 5–10 × 3–6 mm, adaxially green, abaxially light green, sometimes reddish, both surfaces glabrous or pilose, base obliquely truncate, margins finely serrulate above middle, apex obtuse. Cyathia solitary, axillary; peduncle 1–3 mm. Involucre turbinate, 1 × 1 mm, with 4 triangular marginal lobes; glands 4, oblong; appendages white or pink-red. Staminate flowers many, as high as cup. Pistillate flowers: ovary 3-angular-ovoid, smooth and glabrous; styles free, persistent; stigma 2-lobed. Capsules 3-angularovoid-globose, 2.0 × 2.2 mm, smooth. Seeds 3-angular-ovoid-globose, 1.3 × 0.9 mm, grey, smooth.

Iconography:— Pignatti et al. (2017: 323), Pahlevani & Riina (2011: 309, Fig. 3), Benedì & Orell (1992a: 25, Fig. 6, under the name Chamaesyce humifusa ), Hegi (1924: 144, Fig. 1756), Fig. 13.

Chromosome number:—2n = 22 ( Ma & Gilbert 2008, Löve & Löve 1961).

Ecology:—Accidentally dispersed by humans and other animals as contaminant; globally considered as weed of cereals, ornamental gardens and nurseries. It commonly grows on stony roadsides and disturbed grounds ( Pahlevani & Riina 2011).

Alien status:—Neophyte native to the temperate Asia and perhaps Eastern Europe (Crimean Peninsula, Ukraine and South-East of European Russia), it can be considered as naturalized in Italy. First European records were for Germany in the second half of XIX century. Nowadays, it is considered as naturalized in Middle and South Europe. First Italian records were probably from EMR and UMB in the 80s of XIX century ( Thellung 1907, Saccardo 1909).

Occurrence in Italy:—All Italian regions, excluding VDA: casual in LIG, TOS, CAM, PUG, and CAL; naturalized in all the other regions. In Galasso et al. 2018a the status of the species for TOS is naturalized. However, according to the extensive analysis of herbarium material and field investigation, we consider the species as casual in TOS (see also Temporal variation of distributions in Tuscany).

Taxonomic annotations:— Euphorbia humifusa has often been quite confused with E. serpens , E. chamaesyce , and E. glyptosperma (see taxonomic annotations of E. chamaesyce , E. glyptosperma and E. serpens ).

Type designation:—As suggested by Hodvina (2008) the Supplementum was distributed before January 1 of 1814, so that the protologue should be ascribed to Willdenow (1813). Moreover, we note that the author of the species is Willdenow himself, as reported in WCSP (2018), and not Schlechtendal as reported by Galasso et al. (2018a). Euphorbia humifusa was described as a species occurring in Botanical Garden of Berlin. In Willdenow’s collection (B-W), we retrieved only one specimen of E. humifusa (B-W 9283-01.0), reporting his initials and handwriting, thus justifying its eligibility as lectotype. Radcliffe-Smith (1982) already referred to this herbarium specimen, but not indicating it as type material (according Jarvis et al. 2001, Radcliffe-Smith used to explicitly indicate type material).