Euphorbia subg. Chamaesyce, Linnaeus, 1753

Mifsud, Stephen, 2018, Contribution to the flora of the Maltese Islands: Euphorbia subg. Chamaesyce and Euphorbia exigua s. l. (Euphorbiaceae), Phytotaxa 372 (2), pp. 153-166 : 160

Key to the species of Euphorbia subg. Chamaesyce occurring in Malta (bold type) and closely related species

1 Plants suberect or procumbent; leaflets more than 16 mm long, well-spaced...................................................................................2 from each other along the rachis ..........................................................................................................................................................

- Plants completely prostrate; leaflets less than 15 mm long, close to each other................................................................................3

2 Plant completely glabrous; fruit up to 1.4 mm long; stipules developed .................................................................. E. hypericifolia

- Plant scantly hairy at leaf nodes and base of plant; fruit 1.5–2.0 mm long; stipules rudimentary, inconspicuous, linear and short .. ............................................................................................................................................................................................... E. nutans

3 Fruit glabrous; seeds smooth.............................................................................................................................................................4

- Fruit scantly villous, usually near the keel; seeds rugose or ridged..................................................................................................7

4 Capsule> 3.5 mm long; seeds> 2.5 mm long; habitat sand dunes........................................................................................ E. peplis

- Capsule <3 mm long; seeds <2 mm long; habitat not sand dunes....................................................................................................5

5 Leaves denticulate at the upper half, elongated; stipules filiform.................................................................................... E. humifusa

- Leaves entire, rounded, slightly longer than wide; stipules deltate in outline ....................................................... E. serpens s.l. ›› 6

6 Stipule entire, deltate, scar-like ........................................................................................................................................ var. serpens

- Stipule lacerated or deeply lobed ............................................................................................................................... var. fissistipula

7 Many leaves with conspicuous, central, elongated red markings .................................................................................... E. maculata

- Leaves green or at most with a small or faded red spots or short stripe.............................................................................................8

8 Fruit hairy on the keels only; plant densely villous throughout ...................................................................................... E. prostrata

- Fruit hairy throughout or completely glabrous in rare cases; plant glabrous or scantly hairy at the stem and leaf internodes........9

9 Leaves oblong-lanceolate, circa twice as long as wide; seeds transversely grooved....................................................... E. maculata

- Leaves more rounded-ovate (length:width <2); ................................................................................................... E. chamaesyce s l. seeds rugulose throughout................................................................................................................................................................10

10 Nectary glands with an irregularly serrulate margin, wider than its length ............................................................. var. chamaesyce

- Nectary glands lobed with distinct sinuses, as long or longer than wide.................................................................. var. massiliensis