1A.	Leaflets 10 mm wide or wider	2
1B.	Leaflets less than 5 mm wide	3
2A.	Leaflets 1 pair per pinna, 2–5 cm wide	S. crassifolia
2B.	Leaflets 4 or more pairs per pinna, 9 mm wide or less	S. anisophylla
3A.	Inflorescences arranged in spikes, 2–6 times longer than wide	4
3B.	Inflorescences arranged in spheric capitula or ovoid capitula, less than twice as long as wide	5
4A.	Leaflets 5–9 (-12) mm long, petiole (4-) 6–11 mm long; inflorescence lax; fruit not curling when mature; seeds suborbicular, 7–10 mm long	S. wrightii
4B.	Leaflets 3–6 mm long, petiole 2–5 mm long; inflorescence dense; fruit curling when mature; seeds orbicular, 5–7 mm long	S. greggii
5A.	Leaflets 15–35 pairs per pinna; fruit coriaceous, velvety pubescent	S. berlandieri
5B.	Leaflets 6–20 pairs per pinna	6
6A.	Leaflets 15–20 pairs per pinna; pinnae 2–7 pairs per leaf	S. × emoryana
6B.	Leaflets 6–13 pairs per pinna; pinnae 2–4 pairs per leaf	7
7A.	Leaflets cuneate-oblong, glaucous, with obvious veins, not strongly reticulated abaxially (down surface)	S. roemeriana
7B.	Leaflets widely oblong, light green, strongly reticulated abaxially	S. micrantha