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Roemer senna, twoleaf senna, twoleaf wild sensitive plant

twinleaf senna

Habit Herbs, perennial, to 0.7 m. Leaves slightly sclerophyllous, 2.5–9.5 cm, hairy; stipules caducous; extrafloral nectary 1, between leaflet pair, shortly stipitate; leaflet pairs 1, blades lanceolate-oblong or lanceolate, 20–70 × 4–14 mm. Herbs, perennial, to 0.4 m. Leaves slightly sclerophyllous, 1.5–5.5 cm, hairy; stipules caducous; extrafloral nectary 1, between leaflet pair, stipitate or subsessile; leaflet pairs 1, blades obliquely oblong or ovate-oblong, 8–46 × 5–16 mm.
Racemes

1–5-flowered;

bracts caducous.

1–3-flowered;

bracts caducous.

Pedicels

9–16 mm.

3–11 mm.

Flowers

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.

monosymmetric;

calyx caducous, yellowish to pale green;

corolla yellow, longest petal 5–10 mm;

androecium not heterantherous, stamens 7, staminodes 3;

anthers to 1.8–2.8 mm, dehiscing by 1 apical pore, apical appendage 0;

gynoecium nearly linear, ovules 22–36;

ovary densely hairy;

style incurved, to 1.5 mm, distally dilated.

Legumes

erect, subcylindrical, straight or slightly curved, 20–35 × 4.5–6.5 mm, corrugated over seeds, dehiscing apically downward.

erect, cylindrical, curved, 17–30(–50) × 4.5–6.5 mm, slightly corrugated over seeds, dehiscing apically downward.

Seeds

brown or pinkish brown, paddle-shaped or pyriform.

brownish olive green becoming gray, paddle-shaped to pyriform.

2n

= 28.

Senna roemeriana

Senna bauhinioides

Phenology Flowering spring–early fall. Flowering mid spring–mid fall.
Habitat Mesquite grasslands, chaparral, draws in shortgrass prairies, barren hillsides, desert washes, roadsides. Stony hillsides, plains, bajadas, dry washes.
Elevation 100–2000 m. (300–6600 ft.) 100–1800 m. (300–5900 ft.)
Distribution
from FNA
NM; OK; TX; Mexico (Chihuahua, Coahuila, Nuevo León)
[WildflowerSearch map]
[BONAP county map]
from FNA
AZ; NM; TX; Mexico (Chihuahua, Coahuila, Nuevo León, Sonora)
[WildflowerSearch map]
[BONAP county map]
Discussion

Senna bauhinioides is one of three sennas in North America that can form and sprout from a woody taproot (along with S. pumilio and S. ripleyana; H. S. Irwin and R. C. Barneby 1982).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 11. FNA vol. 11.
Parent taxa Fabaceae > subfam. Caesalpinioideae (excluding Mimosoid clade) > Senna Fabaceae > subfam. Caesalpinioideae (excluding Mimosoid clade) > Senna
Sibling taxa
S. alata, S. armata, S. artemisioides, S. atomaria, S. bauhinioides, S. corymbosa, S. covesii, S. durangensis, S. hebecarpa, S. hirsuta, S. ligustrina, S. lindheimeriana, S. marilandica, S. mexicana, S. multiglandulosa, S. obtusifolia, S. occidentalis, S. orcuttii, S. pendula, S. pilosior, S. pumilio, S. ripleyana, S. surattensis, S. wislizeni
S. alata, S. armata, S. artemisioides, S. atomaria, S. corymbosa, S. covesii, S. durangensis, S. hebecarpa, S. hirsuta, S. ligustrina, S. lindheimeriana, S. marilandica, S. mexicana, S. multiglandulosa, S. obtusifolia, S. occidentalis, S. orcuttii, S. pendula, S. pilosior, S. pumilio, S. ripleyana, S. roemeriana, S. surattensis, S. wislizeni
Synonyms Cassia roemeriana, Earleocassia roemeriana Cassia bauhinioides, Earleocassia bauhinioides
Name authority (Scheele) H. S. Irwin & Barneby: Mem. New York Bot. Gard. 35: 282. (1982) (A. Gray) H. S. Irwin & Barneby: Phytologia 44: 499. (1979)
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