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Key to Lithospermum

Boraginaceae

Lithospermum

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1
Corolla lobes acute to acuminate, erect (continuing the plane of the corolla tube); style exserted.
  2
Corolla lobes yellow to orange; nutlet 2.0-2.8 mm long; corolla lobes either 2.5-4× as long as wide and acuminate (L. virginianum) or 1.5-2× as long as wide, acute (O. decipiens).
    3
Stem hairs 2.5-5.0 mm long; corolla lobes 1.5-2× as long as wide, acute; tips of the anthers reaching the base of the corolla sinuses; [endemic to Ketona dolomite glades, Bibb County, c. AL]
 ⇒ Lithospermum decipiens
    3
Stem hairs < 2.0 mm long; corolla lobes 2.5-4× as long as wide and acuminate; tips of the anthers below the corolla sinuses; [widespread in our area]
 ⇒ Lithospermum virginianum
  2
Corolla lobes dull greenish-white; nutlet 2.5-3.0 mm long; corolla lobes 1.5-2× as long as wide, acute.
    4
Leaf vestiture solely of dense appressed hairs on both surfaces (the plant appearing ashy-white)
 ⇒ Lithospermum molle
    4
Leaf vestiture at least in part of spreading or ascending hairs.
      5
Stems glabrescent (with widely scattered appressed hairs) below the inflorescence branches
 ⇒ Lithospermum subsetosum
      5
Stems persistently and obviously pubescent below the inflorescence branches.
        6
Upper leaf surface with hairs of similar length, these appressed to ascending; corolla 11-20 mm long; nutlets tapered to the base, lacking a collar; longest stem hairs near midstem < 2.2 mm long
 ⇒ Lithospermum occidentale
        6
Upper leaf surface with hairs of two lengths, these spreading; corolla either 6-10 mm or 11-20 mm long; nutlets either flared at the base (forming a collar) or rounded to the base (lacking a collar); longest stem hairs near midstem either 2-4 mm long or < 2.2 mm long.
          7
Corolla 11-20 mm long; nutlets rounded and not at all constricted at the base; stem pubescence 2-4 mm long
 ⇒ Lithospermum onosmodium
          7
Corolla 6-10 mm; nutlets flared at the base, forming a collar; longest stem hairs near midstem < 2.2 mm long
 ⇒ Lithospermum parviflorum
1
Corolla lobes rounded, spreading; style included.
  8
Corolla white or yellowish-white, the tube 4-8 mm long.
    9
Plant with basal rosette; lower cauline leaves about equal in size to the upper cauline leaves; leaves acute to obtuse
 ⇒ Lithospermum tuberosum
    9
Plant lacking basal rosette; lower cauline leaves smaller than the upper cauline leaves; leaves acuminate or acute.
      10
Upper stem internodes mostly 3-6 cm long; leaves mostly > 2 cm wide, acuminate
 ⇒ Lithospermum latifolium
      10
Upper stem internodes mostly 1-2 cm long; leaves mostly < 2 cm wide, acute
 ⇒ Lithospermum officinale
  8
Corolla yellow-orange, the tube 7-30 mm long.
      12
Plant with dense, soft, appressed pubescence, the hairs usually without pustular bases; calyx lobes 6-8 mm long at maturity; nutlets 2-3 mm long; [mostly of rocky or clayey circumneutral soils of inland physiographic provinces]
 ⇒ Lithospermum canescens
      12
Plant with scattered, stiff, spreading pubescence, the hairs with or without pustular bases; calyx lobes 10-15 mm long at maturity; nutlets 3.5-4.5 mm long; [variously of sandy acidic soils of the Coastal Plain or inland].
        13
Pubescence with slender bases; mature calyx lobes flat; plants with 15-25 well-developed leaves below the inflorescence; [of sandy Coastal Plain habitats from se. VA southward]
 ⇒ Lithospermum caroliniense
        13
Pubescence with pustular bases; mature calyx lobes strongly keeled; plants with (30-) 35-45 well-developed leaves below the inflorescence; [inland, known from inland provinces, PA, OH, IN, KY, IN, IL, MO, AR, and OK]
 ⇒ Lithospermum croceum