Key to Aristida

View taxon page for Aristida

(For a list of species in Aristida, use the above link.)

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

1. Lower stems densely hairy ..... A. californica

1' Lower stems glabrous

2. Annual

3. Glumes 10–22 mm; 

lemma 

In Poaceae, the lower, generally larger of two sheathing bracts subtending a flower, generally ensheathing the palea (in a sterile lemma, the associated flower and sometimes palea are rudimentary or absent); with the palea and flower, comprising the floret.

 

awns 

1. Bristle-like appendage or elongation, generally terminal. 2. Stiff, needle-like pappus element in Asteraceae.

generally 10–70 mm ..... A. oligantha

3' Glumes 3–13 mm; lemma awns 3–20 mm

4. Central 

awn 

1. Bristle-like appendage or elongation, generally terminal. 2. Stiff, needle-like pappus element in Asteraceae.

straight to curved at base ..... A. adscensionis

4' Central awn spirally coiled at base ..... A. dichotoma

2' Perennial herb

5. 1° inflorescence branches 

spreading 

Oriented more or less perpendicularly to the axis of attachment; often, more or less horizontal.

at base (upper 

appressed 

Parallel or nearly parallel to and often in contact with surface of origin; used to describe the disposition of hairs, leaves, pedicels, etc.

to 

ascending 

Curving or angling upward from base, or about 30-60 degrees less than vertical or away from axis of attachment.

in Aristida purpurea var. wrightii)

6. Lower inflorescence branches spreading, upper ascending to appressed ..... A. purpurea var. parishii (2)

6' All inflorescence branches spreading

7. Leaf 

blade 

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

base glabrous; lemma tip much twisted; anthers 0.8–1 mm ..... A. divaricata

7' Leaf blade base sparsely long-hairy; lemma tip slightly twisted or straight; anthers 1–2 mm ..... A. ternipes var. gentilis

5' 1° inflorescence branches appressed to ascending at base (curving or drooping in Aristida purpurea var. purpurea) ..... A. purpurea

8. Awns generally > 40 mm

9. Upper 

glume 

In Poaceae, each of generally two sheathing bracts that are the lowermost parts of a spikelet, subtending one or more florets.

generally 16–25 mm; lemma 0.3–0.8 mm wide just below awns, awns 0.2–0.5 mm wide at base ..... var. longiseta

9' Upper glume generally 7–16 mm; lemma 0.1–0.3 mm wide just below awns, awns 0.1–0.3 mm wide at base ..... var. purpurea (2)

8' Awns generally < 40 mm

10. 1° inflorescence branches and 

spikelet 

1. In Poaceae, one or more florets (each a flower with subtending lemma and generally palea) and generally 2 subtending glumes; in a sterile spikelet, the flower(s) and sometimes palea(s) are rudimentary or absent. 2. In Cyperaceae, the smallest aggregation of flowers (generally more than 2) and associated bracts.

stalks thread-like, curving to drooping, appearing S- or U-shaped ..... var. purpurea (2)

10' 1° inflorescence branches and spikelet stalks generally stiff, straight, generally appressed to ascending (lower spreading in Aristida purpurea var. parishii)

11. Lemma tip, awn base ± 0.1 mm wide at base, awns delicate ..... var. nealleyi

11' Lemma tip, awn base 0.2–0.3 mm wide, awns ± stiff

12. Inflorescence generally 3–15 cm; 

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 generally 4–10 cm ..... var. fendleriana

12' Inflorescence generally 12–30 cm; leaf blade generally 10–25 cm

13. Inflorescence dense, ± red when young; lower branches with 10–20 

spikelets 

1. In Poaceae, one or more florets (each a flower with subtending lemma and generally palea) and generally 2 subtending glumes; in a sterile spikelet, the flower(s) and sometimes palea(s) are rudimentary or absent. 2. In Cyperaceae, the smallest aggregation of flowers (generally more than 2) and associated bracts.

..... var. parishii (2)

13' Inflorescence ± open, tan to brown when young; lower branches with 2–10 spikelets ..... var. wrightii

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