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Key to Gentianaceae

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1 Leaves all scale-like, 1-3 (-5) mm long, appressed to the stem.
  2 Plants green or purplish-brown, with chlorophyll (hemimycoheterotrophic); [tribe Gentianeae, subtribe Swertiinae]
  2 Plants white or cream, lacking chlorophyll (holomycoheterotrophic); [tribe Voyrieae]
1 Leaves larger, spreading or ascending.
    3 Stem leaves whorled; plants robust, 1-3 m tall; [tribe Gentianeae, subtribe Swertiinae]
    3 Stem leaves opposite; plants generally < 1 m tall.
      4 Calyx lobes 0 (or interpretable as 2) or 4-5; corolla pink, blue, white.
image of plant
Show caption*© Richard & Teresa Ware
        5 Calyx lobes 0 (but the flower subtended by 2 leaflike bracts that have sometimes been interpreted as sepals); stem leaves obovate, widest near the rounded tip), 0.5-1.5 cm long, crowded near the tip of the stem, basal rosette never present; [of nutrient-rich, mesic forests]; [tribe Gentianeae, subtribe Swertiinae]
image of plant
Show caption*© Scott Ward
        5 Calyx lobes 4-5; stem leaves lanceolate, ovate, elliptic or narrowly elliptic (widest near the middle or toward the base, the tip acute or acuminate), mostly > 1.5 cm long, distributed fairly evenly along the stem, basal rosettes sometimes present; [of various more-or-less open habitats (except some species of Gentiana, which can occur in nutrient-rich, mesic forests)].
          6 Corolla lobes 5-14, longer than the corolla tube, pink or white; [common natives]; [tribe Chironieae, subtribe Chironiinae].
             7 Stigmas shorter than the style
             7 Stigmas equaling or longer than the style
          6 Corolla lobes 4-5, shorter than the corolla tube, blue, lavender, pink or white.
               8 Corolla tube < 2 mm wide; [rare to uncommon exotics, naturalized in disturbed areas]; [tribe Chironieae, subtribe Chironiinae].
                 9 Style not divided or subcapitate; stigma lobes rhombic to fan-shaped, not fleshy; capsule elliptic to ovoid
                   10 Corolla lobes alternating with corolla appendages (appearing as plaits or lobes, these often toothed, notched, or lacerate, sometimes as long as or longer than the true corolla lobes); main stem leaves cuneate at the base; perennial; [tribe Gentianeae, subtribe Gentianinae]
                   10 Corolla lobes not alternating with corolla appendages; main stem leaves rounded to cordate at the base; biennial or annual; [tribe Gentianeae, subtribe Swertiinae].
                     11 Corolla lobes 4, finely fringed; main stem leaves rounded at base, with lateral veins obscure; biennial
                     11 Corolla lobes 5, entire, not fringed; main stem leaves cordate (the cordate bases often overlapping the opposite leaf), with 2-3 well-developed lateral veins (prominently visible on the lower surface); annual

Key P1: herbaceous dicots with alternate, simple, and unlobed leaves on the stem

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1 Inflorescence an involucrate head subtended by phyllaries, the heads solitary or many and variously arrayed in secondary inflorescences, the ovary inferior, the corolla connate and tubular at least basally, the calyx absent, the stamens 5, the fruit a cypsela
1 Inflorescence, flower, and fruit structure various, but not with the combination of features as above (sometimes the flowers in a head, e.g. Eryngium in APIACEAE, but then with other features differing, such as stamens 4, or green calyx present, or fruit a schizocarp of mericarps, etc.).
  2 Perianth uniseriate (represented only by undifferentiated tepals or sepals; look at the front and back of the flowers for two layers) or completely absent; flowers usually unisexual, less commonly bisexual).
    3 Inflorescence a cyathium, consisting of a single pistillate flower (reduced to a single 3-carpellate pistil) and 2 or more staminate flowers (each reduced to 1 stamen), borne in a cup-like involucre, the involucre bearing pointed or rounded glands, these sometimes brightly colored and petaloid, mimicking an individual flower (the cyathia then secondarily arranged in terminal cymes, or solitary and axillary, etc.); fresh plants with milky juice; fruit a 3-lobed, 3-locular capsule
    3 Inflorescence not a cyathium (and staminate or bisexual flowers with > 1 stamen; fresh plants lacking milky juice (except Stillingia in EUPHORBIACEAE); fruit various, not as above.
      4 Leaf margins toothed in some manner (serrate, dentate, crenate, etc.)
        5 Leaf teeth rounded to subacute, resembling shallow lobes, irregular, few (mostly < 6 per leaf side).
          6 Fruit a single-seeded achene or utricle; [plants of various disturbed or saline, usually sunny habitats]
          6 Fruit a 3-lobed, circumscissilely dehiscent capsule; [plants native of rich moist shaded forests or exotics in suburban woodlands]
        5 Leaf teeth sharp to crenate, not lobe-like, regular, many (mostly > 10 per leaf side).
             7 Leaf bases cuneate (or strongly oblique in Begonia, with one leaf base usually being cuneate, the other variously rounded or cordate).
               8 Flowers typically with 2 or 4 (-5) showy, white-colored tepals; leaves sometimes variegated; fruit unequally or subequally 3-winged capsules; [ornamental waifs or uncommon non-natives]
               8 Flowers cyathia, not merely bearing showy tepals; leaf not variegated but sometimes bearing darkened red or black splotches; fruit capsules, but these not conspicuously winged; [natives and non-natives, usually not ornamental]
             7 Leaf bases cordate to rounded.
                 9 Styles 3; fruit a 3-lobed, 3-carpellate capsule (1 carpel sometimes aborting); inflorescence either a terminal or leaf opposed raceme, or a dense axillary condensed cyme with conspicuous toothed bracts subtending the flowers
                 9 Styles 1 or 2; fruit either an achene or a multiple of achenes; inflorescence either an axillary dense cyme (almost a head), or an axillary spike with glomerules, or a terminal or axillary panicle.
                   10 Styles 2; inflorescence a dense axillary cyme (almost a head); fruit a multiple of achenes; plant lacking stinging hairs; [exotic plant of weedy situations]
                   10 Style 1; inflorescence an axillary spikes with glomerules, or a terminal or axillary panicle; plant either with stinging hairs or not; [plant a rare exotic (Boehmeria nivea) or a native of moist forests (Boehmeria cylindrica, Laportea)]
      4 Leaf margins entire.
                     11 Ovary inferior (flowers epigynous, the ovary sitting below the perianth and androecium) or half-inferior (perigynous, the ovary sitting level with the remaining floral parts).
                       12 Leaf base cordate; calyx 3-lobed, fused into a bilaterally symmetrical, curved brown or yellowish tube; fruit a capsule
                       12 Leaf base cuneate, rounded, or truncate; calyx of 3-4-5 distinct sepals, radially symmetrical, white or yellow; fruit a dry, nutlike drupe or an achene.
                          13 Leaves subsessile or very short petiolate, elliptic or narrowly elliptic, broadest near the middle; [native]
                          13 Leaves distinctly petiolate, rhombic, widest near the base; [rarely naturalized exotics].
                              15 Inflorescence a leaf-opposed spike or raceme, the inflorescence arising opposite of stem leaves (except Saururus, whose spikelike racemes are leaf-opposed and/or terminal); flowers visually white from white petaloid sepals, white bracts, or white stamens.
                                16 Sepals present, 4 or 5; petaloid, white; carpels 1 to many (-12); stamens 4 to many (-25); fruit a berry or an apically 2-lobed achene (as in Petiveria); leaf bases cuneate or rounded (but not cordate); [Eudicots].
                                16 Sepals absent; carpels 3-4; stamens 2-6 (-8); fruit a capsule, a 1-seeded drupe, or a schizocarp of 3-4 mericarps; leaf bases cordate or subcordate; [Basal Angiosperms].
                                    18 Fruit a capsule or schizocarp with 3-4 mericarps; stamens 3 or 6-8; plants terrestrial
                              15 Inflorescence not leaf opposed, instead arising with stem leaves (axillary) or terminal, the inflorescence not spikes nor racemes, instead either simpler (single axillary or glomerules of flowers) or more complexly branched (terminal or axilary panicles or terminal complex cymes); flowers white, reddish, scarious, or greenish.
                                       19 Stipules tubular, sheathing (= ocreae); flowers subtended by tubular, sheathing bracteoles (= ocreolae); nodes usually prominently swollen; perianth usually of 5-6 white to pink tepals
                                       19 Stipules not tubular or sheathing; flowers not subtended by ocreolae; nodes not swollen; perianth absent or of 3-5 sepals.
                                             22 Sepals petaloid, pink and relatively conspicuous (although the sepals ca. 1-3 mm in length); plants prostrate to somewhat ascending annuals; leaves opposite or nearly whorled; achenes muricate
                                             22 Sepals not petaloid, inconspicuous, green or greyish in color; plants prostrate or erect, annual or perennial; leaves alternate OR either alternate or opposite (Amaranthaceae); achenes variously textured (smooth or textured, sometimes reticulate or verrucose, but rarely muricate).
  2 Perianth biseriate (represented by differentiated whorls of sepals and petals, the sepals usually green or drab in color, the petals often brightly colored); flowers nearly always bisexual (there are exceptions).
                                                        27 Inflorescence not a dense, leaf-opposed spike, instead a terminal head or variously axillary or terminal (the flowers solitary or not, but not in a dense spike).
                                                          28 Flowers yellow; stamens numerous (15+), monomorphic or heteromorphic (inner and outer of differing length), conspicuously exerted from the flowers, often surpassing the ovary; leaves basally lobed or unlobed (often a mix in M. floridana and M. oligosperma)
                                                          28 Flowers blue or white; stamens fewer (usually < 10), monomorphic, if exerted, the ovary usually still apparent; leaves unlobed.
                                                                 31 Petals 4-7; stamens 1× or 2× as many as the petals, 4-7, 8, 10, 12, or14; leaves herbaceous in texture
                                                                 31 Petals 5 (or sometimes doubled in horticultural forms); stamens 6-40 (or more); leaves fleshy in texture
                                                                   32 Corolla bilaterally symmetrical (zygomorphic), petals connate, at least basally (except distinct in VIOLACEAE); fruit a capsule or legume (the capsule conspicuously spiny in Krameria).
                                                                     33 Petals connate (at least basally), 4, 5, 6, 7, or 8; carpels 1, 2, 4, 5, or 6 (rarely 3 in Reseda in RESEDACEAE); fruit a legume or 1-, 2-, or 5-loculed capsule (except a 1-seeded indehiscent pod in Krameria in KRAMERIACEAE).
                                                                       34 Stamens 6-10 (-25), more than the number (4 or 5) of petals and the number (4 or 5) of the sepals; fruit a legume or a 1-6-carpellate capsule.
                                                                                38 Pistil 2-carpellate; capsule 2 locular, opening gradually or not at all; inflorescence a terminal spike, raceme or panicle (or solitary, axillary flowers in Chaenorrhinum in PLANTAGINACEAE and Krameria in KRAMERIACEAE).
                                                                                    40 Stamens 4; corolla with a distinct spur or sac at the base between the the 2 lower calyx lobes (except not spurred in Digitalis and Schwalbea); capsule loculicidal (only at the summit in Antirrhinum and Chaenorrhinum, and septicidal in Schwalbea); pubescence of the stem and leaves neither gland-tipped (except in Antirrhinum and Chaenorrhinum) nor dendritically branched.
                                                                                        42 Plants herbaceous vines, fleshy and mucilaginous, the leaves variously orbicular, ovate, cordate or sometimes elliptic; fruit utricles (small sacs surrounding an achene), partly to completely enclosed in the persistent, dry to somewhat fleshy perianth; sepals 2
                                                                                             44 Pistils 4-10 (each 1-carpellate) in a ring, these sometimes fused basally, each with its own style/stigma; fruit either an aggregate of achenes or follicles or a 5 (-7) locular capsule.
                                                                                                 46 Fruit an aggregate of follicles; leaves fleshy in texture; inflorescence; leaves entire of sparsely and coarsely serrate, with < 12 points per leaf; [plants primarily of dry habitats]
                                                                                             44 Pistil 1, with 1-to many carpels (in many MALVACEAE, the carpels loosely united in a ring [of more than 5] around the single style/stigma); fruit either a 1-, 2-, 3-, 5-, 6-, or 10-locular capsule, or a silique/silicle, or a ring of mericarps.
                                                                                                        49 Stamens (4-) 5-many, distinct (not forming a staminal tube); carpels 2-5; fruit a capsule; leaves entire (serrate in Croton in EUPHORBIACEAE, distally serrate in Capraria in SCROPHULARIACEAE).
                                                                                                                  54 Leaf margins distally serrate, the surfaces punctate-glandular and also with internal oil-secreting cavities; corolla white (the inside sometimes with scattered purple spots); [s. FL and s. TX only in our flora area]
                                                                                                                                  61 Plants usually strongly gray or white-colored and villous, growing in short, suffrutescent mounds or mats; leaves densely pubescent (hairs densely appressed adaxially, tomentose abaxially); inflorescence of solitary flowers or extra-axillary, never scirpioid; corolla lavender or whitish-lavender, the lobes 1.8-3.0 (-4.5) mm long, broadly rounded; [s. TX, westward; primarily of the Trans-Pecos region]
                                                                                                                                  61 Plants variously glabrous or pubescent (sometimes villous), usually herbaceous, occasionally suffrutescent and mound or mat-forming; inflorescence variously elongate or racemose, often scirpioid (curved or coiled on one side of the inflorescence axis; e.g., Heliotropium), occasionally solitary (e.g., Euploca, in part; although in this case the leaves of the shrubby Euploca are significantly narrower); corolla variously colored (including lavender); [plants collectively widespread, including TX]