Key to Araceae

View taxon page for Araceae

Jepson Manual glossary definitions can be seen by moving your cursor over words underlined with dots.

1. Plants not reduced, clearly differentiated into stems, leaves; floating aquatics or not; inflorescence a 

spike 

1. In flowering plants excluding Asteraceae, Cyperaceae, Poaceae, and some other groups, an unbranched inflorescence in which the flowers are sessile and nearly always open from the bottom to the top of the inflorescence. 2. In Asteraceae, Cyperaceae, Poaceae, and some other groups, a spike-like inflorescence is one in which the inflorescence units (e.g., heads in Asteraceae; spikelets in Cyperaceae and Poaceae), instead of individual flowers, are sessile and attached directly to the main axis of the inflorescence, not to branches, and in which floral development may or may not proceed as in 1.

, conspicuous; perianth parts 0, 4, 6; stamens 0, 2, 3, 4, 6 (genera treated as Araceae in TJM (1993), minus Acorus)

2. Plant aquatic, floating; inflorescence ± 

sessile 

Without a petiole, peduncle, pedicel, or other kind of stalk.

, inconspicuous among 

basal 

At or near the base of a plant or plant part. Especially said of leaves clustered near the ground or of a placenta confined to the base of an ovary.

leaves ..... [PISTIA]

2' Plant terrestrial or near edge of water; inflorescence peduncled, ± conspicuous

3. Petiole < 

leaf 

Organ arising from a stem, generally composed of a stalk (petiole) and a flat, expanded, green, photosynthetic area (blade); distinguished from a leaflet by the presence in its axil of a bud, branch, thorn, or flower; sometimes with lateral, basal appendages (stipules); either simple (toothed, lobed, or dissected but not divided into leaflets) or compound (divided into leaflets).

 

blade 

Expanded portion of a leaf, petal, or other structure, generally flat but sometimes rolled, cylindric, wavy, or cupped.

; inflorescence 

bract 

Reduced, leaf- or scale-like structure subtending a branch, cone scale, peduncle, pedicel, or flower.

yellow ..... LYSICHITON

3' Petiole ± >= leaf blade; inflorescence bract sometimes pale yellow-green but not yellow

4. Peduncle ± >= leaf; inflorescence bract white both surfaces (tip generally pale green) ..... ZANTEDESCHIA

4' Peduncle generally << leaf; inflorescence bract abaxially pale yellow-green, adaxially ± white to pale yellow-green or dark purple, or green both surfaces (margins pale green to white or not)

5. Inflorescence sterile in ± upper 1/2, flowers only in lower 1/2; inflorescence bract abaxially pale yellow-green, adaxially ± white to pale yellow-green or dark purple ..... ARUM

5' Inflorescence fertile throughout; inflorescence bract green both surfaces (margins pale green to white or not) ..... [Peltandra virginica]

1' Plants much reduced, not differentiated into stems, leaves; floating aquatics; inflorescence 1-flowered, inconspicuous; perianth parts 0; stamens 1, 2 (genera treated as Lemnaceae in TJM (1993))

6. Roots 0 (see also Lemna trisulca)

7. Plant body ± 

cylindric 

Elongate, with parallel sides and, at any point, round in transverse section.

to nearly spheric, 0.4–1.3 mm ..... WOLFFIA

7' Plant body flat, 

linear 

Elongate, with nearly parallel sides; narrower than elliptic or oblong.

to 

oblong 

Longer than wide, with nearly parallel sides; wider than linear.

, 3–10 mm ..... WOLFFIELLA

6' Roots present

8. Root generally 1 ..... LEMNA

8' Roots generally 2–16

9. Roots generally 2–7; plant body 3–5 mm, veins 3–7; winter 

buds 

1. An incompletely developed, more or less embryonic shoot, usually covered with bud scales. 2. An unopened flower, often protected by sepals.

0 ..... LANDOLTIA

9' Roots generally 7–16; plant body 5–10 mm, veins 7–12; winter buds produced ..... SPIRODELA

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