Key to Tetradymia

View taxon page for Tetradymia

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

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

1. Stem unarmed (leaves not forming spines)

2. Flowers (5)6–9 per 

head 

1. A dense, often spheric inflorescence of sessile or subsessile flowers.
2. In Asteraceae and some other groups, a head-like inflorescence is one in which sessile or subsessile inflorescence units (e.g., heads in Asteraceae, umbels enclosed by involucres in Eriogonum), instead of individual flowers, are attached in a short dense cluster without an evident axis or branches.

; pappus 0 (but fruit covered with long, pappus-like hairs); 

axillary 

Pertaining to or within an axil, especially a leaf axil.

 

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).

clusters generally 0 ..... T. comosa (2)

2' Flowers 4(5) per head; pappus present; axillary leaf clusters generally present

3. Main leaves 

tomentose 

Covered with densely interwoven, generally matted hairs.

or silvery; clustered leaves ± (ob)lanceolate ..... T. canescens

3' Main leaves glabrous or sparsely tomentose; clustered leaves thread-like to linear-oblanceolate

4. Main leaves narrowly awl-shaped, stiffly 

ascending 

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

or 

appressed 

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

, generally 5–10 mm; clustered leaves generally 3–10 mm, glabrous; fruit generally 3–4 mm, short-stiff-hairy; pappus of ± 100 bristles ..... T. glabrata

4' Main leaves ± thread-like, soft, 10–40 mm; clustered leaves generally 10–20 mm, loosely tomentose; fruit 5–6 mm, long-soft-hairy; pappus of ± 20 stiff bristles or slender scales (± hidden by fruit hairs) ..... T. tetrameres

1' Stem armed with spines derived from main leaves

5. Fruit glabrous, 2.5–3.5 mm ..... T. argyraea

5' Fruit ± long-soft-hairy, 4–8 mm

6. Main leaves narrowly (ob)lanceolate, finally deciduous, base not hardened; pappus 0 ..... T. comosa (2)

6' Main leaves 

tapered 

Gradually (not abruptly) narrower or smaller at base or tip.

to tip, persistent as stout spines, base expanded, hardened; pappus present

7. Clustered leaves tomentose or silvery-hairy; fruit ± short-hairy; pappus of many fine bristles 9–12 mm ..... T. stenolepis

7' Clustered leaves ± glabrous; fruit densely long-hairy; pappus of ± 25 slender scales 6–9 mm

8. Spines sharply 

recurved 

Gradually curved downward or backward.

, 5–25 mm, tomentose; 

involucre 

Group of bracts more or less held together as a unit, subtending a flower, fruit (acorn cup), or inflorescence.

generally 8–12 mm, ± bell-shaped; fruit generally 6–8 mm ..... T. spinosa

8' Spines straight, (1)2–5 cm, becoming glabrous; involucre generally 7–9 mm, obconic; fruit generally 4–5 mm ..... T. axillaris

9. Involucre and 

peduncle 

Stalk of an individual flower borne singly, not in an inflorescence, or of an entire inflorescence, or the corresponding structure in fruit; the stalk subtending an involucre (e.g., in Asteraceae, Polygonaceae).

glabrous; fruit hairs generally 6–8 mm ..... var. axillaris

9' Involucre and peduncle tomentose; fruit hairs generally 9–11 mm ..... var. longispina

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