Senna roemeriana
Senna artemisioides
Roemer senna, twoleaf senna, twoleaf wild sensitive plant
silver senna
1–5-flowered;
bracts caducous.
2–10-flowered;
bracts early caducous.
9–16 mm.
4–15 mm.
monosymmetric;
calyx caducous, pale green;
corolla yellow or orange-yellow, longest petal 12–17 mm;
androecium not heterantherous, stamens 7, staminodes 3;
anthers 2.2–3.3 mm, dehiscing by 1 apical pore, apical appendage 0;
gynoecium nearly linear, ovules 22–40;
ovary densely hairy;
style slightly incurved.
slightly asymmetric, enantiostylous;
calyx yellowish to greenish;
corolla yellow, longest petal 6–10 mm;
androecium not heterantherous, stamens 10, staminodes 0;
anthers 1.5–5 mm, dehiscing by 2 pores, apical appendage 0;
gynoecium incurved, ovules unknown;
ovary slightly hairy;
style slightly incurved.
erect, subcylindrical, straight or slightly curved, 20–35 × 4.5–6.5 mm, corrugated over seeds, dehiscing apically downward.
pendulous, flat, straight or slightly curved, 20–80 × 6–12 mm, corrugated over seeds, indehiscent.
brown or pinkish brown, paddle-shaped or pyriform.
dark brown or dull, obovoid.
= 28.
= 28, 56.
Senna roemeriana
Senna artemisioides
Due to its remarkable morphological and genetic variation (especially in leaflet number and form), Senna artemisioides has a shifting taxonomic history. The species, as circumscribed by Randell, was divided into several morphological forms by B. R. Randell and B. A. Barlow (1998). Senna artemisioides, as presented here, encompasses four common morphological forms found in North America: subsp. filifolia Randell, subsp. petiolaris Randell, nothosubsp. sturtii (R. Brown) Randell, and subsp. zygophylla Randell. D. E. Symon (1998) considered individuals of subsp. petiolaris characterized by arcuate phyllodes to be a separate species, S. phyllodinea (R. Brown) Symon, mainly because of the absence of individuals with an intermediate leaf morphology transitioning to the phyllode shape. Although this argument is reasonable, S. phyllodinea has not been accepted and adopted in other floristic studies. It must be noted that phyllodes consist of the lateral compression of both the petiole and the rachis, and not only of the petiole, as reported by Randell and Barlow. Along the adaxial margin of the phyllode, there is, in fact, a reduced extrafloral nectary at each insertion place of the suppressed leaflets.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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