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Key to Arnoglossum

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1 Larger leaves palmately veined, cordate at the base, either strongly toothed or lobed.

2 Leaves glaucous beneath; stem glaucous and terete (or slightly striate)  Arnoglossum atriplicifolium

2 Leaves green beneath; stem green and conspicuously grooved  Arnoglossum reniforme

1 Larger leaves parallel-veined (the primary veins parallel and converging toward the leaf apex), lanceolate to elliptic-lanceolate, cuneate at the base, entire to remotely toothed (usually fewer than 10 teeth per leaf).

3 Phyllaries not wing-keeled; stem terete.

4 Basal and lower cauline leaves linear to lanceolate, green to slightly glaucous beneath; plants 0.5-2.5 m tall; [usually of pine savannas, se. NC south to s. FL, west to e. TX]  Arnoglossum ovatum var. lanceolatum

4 Basal and lower cauline leaves ovate to ovate-lanceolate, glaucous beneath; plants 1.5-2.5 m tall; [usually of shaded, moist to bottomland habitats, e. GA west to e. LA]  Arnoglossum ovatum var. ovatum

3 Phyllaries wing-keeled; stem strongly angled or sulcate.

5 Basal and low-cauline leaves truncate or subcordate at the base; larger leaves irregularly angulate-lobed or toothed, often somewhat hastate at the base; corolla usually pale lavender  Arnoglossum diversifolium

5 Basal and low-cauline leaves cuneate at the base; larger leaves entire, crenate, sinuate, but not lobed or hastate; corolla creamy yellow (or greenish or tinged with pink).

Show caption*© Scott Allen Davis, some rights reserved (CC BY), uploaded by Scott Allen Davis           6 Phyllary wings highest toward the base; phyllary wings chalky white, erose; leaves with main lateral veins running with the midrib for 2-4 cm into the blade before diverging; [of FL Panhandle]  Arnoglossum album

Show caption*© Scott Ward           6 Phyllary wings uniform or highest toward the tip; phyllary wings pale green, entire; leaves with main lateral veins diverging from the midrib at or very near the base of the blade, not concurrent; [collectively more widespread].

Show caption*© Scott Ward              7 Involucres 12-15 mm high; corollas (9-) 11-12 mm long  Arnoglossum floridanum

7 Involucres 8-14 mm high; corollas 7-11.5 mm long.

Show caption*© Aidan Campos                8 Involucres (9.5-) 10-12 (-14) mm high; corollas 8-10 (-11.5) mm long; leaves usually with 7-9 main parallel veins; mid-stem leaves petiolate, with rounded bases)  Arnoglossum plantagineum

Show caption*© Janet Wright, some rights reserved (CC BY-NC), uploaded by Janet Wright                8 Involucres (8-) 9.5-10 (-12) mm high; corollas 6-8 (-9.5) mm long; leaves usually with 3-5 main parallel veins; mid-stem leaves sessile, with broadly cuneate bases  Arnoglossum sulcatum