Flora of North America species comparison

erect to ascending, branched from base;

branches arcuate or, occasionally, almost prostrate.

erect or ascending, branched from base or nearly so;

branches straight or slightly arcuate (proximal ones sometimes almost prostrate).

alternate;

blade linear, mostly 1–2 mm wide in herbarium specimens, fleshy, usually not swollen at base, apex ± acuminate into rather firm, 1–1.5(–2.2) mm spine.

(especially proximal ones) mostly opposite;

blade linear, usually more than 1.5 mm wide in herbarium specimens, fleshy, distinctly swollen or ovate at base, apex mucronulate, not spinose.

interrupted at maturity, usually 1-flower per axil of bract;

bracts alternate, not imbricate at maturity, reflexed, not distinctly swollen at base, apex narrowing into subulate spine.

distinctly interrupted, 1-flowered;

bracts alternate or almost opposite, not imbricate, horizontally reflexed at maturity, swollen at base, abruptly narrowing into mucronulate nonspinose apex.

bracteoles free or becoming connate and adnate to perianth base;

perianth segments with comparatively narrow wing or in lower flowers occasionally wingless (in S. kali subsp. pontica sometimes prominently winged), with weak or firm, acute apex, glabrous; fruiting perianth 4–6(–8) mm diam. 2n = 36.

bracteoles distinct, not adnate to perianth segments;

perianth segments wingless or with rudimental triangular tubercles at maturity, margins crenate or pectinate-ciliate apically, glabrous; fruiting perianth ca. 3–6(–7) mm diam. 2n = 18.