Croptilon hookerianum

(Torrey & A. Gray) House

Bull. New York State Mus. Nat. Hist. 223: 61. 1921.

Common names: Hooker’s scratchdaisy
Endemic
Basionym: Isopappus hookerianus Torrey & A. Gray Fl. N. Amer. 2: 239. 1842
Synonyms: Croptilon divaricatum var. hookerianum (Torrey & A. Gray) Shinners Haplopappus validus subsp. torreyi E. B. Smith
Treatment appears in FNA Volume 20. Treatment on page 229.
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Stems erect, 20–80(–120) cm. Cauline leaf blades lanceolate to linear, reduced distally (becoming bractlike near heads), margins usually serrate apically, rarely entire. Peduncles stipitate-glandular, sometimes hispid as well. Involucres campanulate, (3.5–)5–8(–10) mm diam. Ray florets (10–)13–21(–29); corolla laminae 6–12 mm. Disc florets (20–)33–70(–108). 2n = 10, 12, 14.

Discussion

Varieties 3 (3 in the flora).

Morphologic differences among the three varieties are slight and they form a closely coherent group within the genus; corresponding differences in geography, habitat, and chromosome number provide a rationale for maintaining the taxonomic and nomenclatural distinctions. B. L. Turner et al. (2003, vol. 1) treated var. hookerianum as including var. graniticum. B chromosomes sometimes are present and appear to increase the number by a pair (E. B. Smith 1966).

Selected References

None.

Key

1 Peduncles long-stipitate-glandular (longest hairs 0.4–0.5 mm, including gland), often slightly hispid proximal to heads; ray laminae 1–2.5 mm wide Croptilon hookerianum var. validum
1 Peduncles short-stipitate-glandular (longest hairs 0.2–0.3 mm, including gland), never hispid; ray laminae (1.2–)2–3(–4) mm wide > 2
2 Peduncles densely stipitate-glandular; ray laminae 1.2–2.2 mm wide; sandy habitats Croptilon hookerianum var. hookerianum
2 Peduncles sparsely stipitate-glandular; ray laminae (1.5–)2–3(–4) mm wide; granitic habitats Croptilon hookerianum var. graniticum