Calycadenia pauciflora A. Gray

Calycadenia pauciflora is variable and closely related to and intergrades with C. fremontii. It is found mostly in the foothills of the Coast Ranges from Tehama County to Lake, Napa, and Yolo counties. It is also known from one location on the valley floor in Butte County.

The morphologic and chromosomal similarity of some populations of Calycadenia ciliosa to C. fremontii led R. L. Carr and G. D. Carr (1983) to merge the two species. Traditional treatments of these taxa and C. pauciflora have placed together populations that are far from homogeneous and may vary from one another in morphology and chromosome number and structure. For instance, C. fremontii and C. pauciflora are each known to include at least six different chromosome races. In this treatment, we have chosen to recognize the larger-headed members of C. pauciflora in the sense of G. D. Carr (1975) as C. fremontii. This reflects the current state of our knowledge, including molecular studies (B. G. Baldwin and S. Markos 1998). Molecular studies have provided a separate means of assessing relationships and insights into the evolution of the genus. Providing a practical taxonomic framework that reflects what is now known about the complicated morphologic and chromosomal patterns of variation of C. pauciflora and C. fremontii has proved to be an elusive goal.

Plants 10–50 cm; self-incom-patible. Stems branched (plants without obvious main axes, branches usually relatively many, slender, usually divergent, often zigzag), finely strigose (some hairs longer). Leaves mostly alternate, 1–5 cm (proximal), ± hispidulous and ± long-hairy (proximal margins and adaxial faces). Heads borne singly or in open, spiciform arrays (1–4 per node). Peduncular bracts ± linear to narrowly elliptic to oblanceolate, 2–3 mm (hispidulous, ± bristly and/or pectinate-fimbriate), apices rounded to truncate, tack-glands 1–3+. Phyllaries 4–6 mm, abaxial faces scabrous, ± strongly bristly, ± shaggy long-hairy on distal margins, tack-glands (0–)1–7+. Paleae 4–6 mm (receptacular cups ± clavate to fusiform, lengths ± 2 times diams.). Ray florets 1(–2); corollas white to reddish, tubes ca. 2 mm (papillate), laminae 5–7 mm (central lobes equaling or slightly narrower than laterals, ± elliptic or distally broader and more rounded, symmetric or nearly so, widest near or beyond middles, sinuses nearly equaling laminae). Disc florets 2–5; corollas white to pinkish, ca. 5–6 mm. Ray cypselae 2.5–4 mm, smooth, usually glabrous, sometimes hairy distally, sometimes with slightly elevated areolae. Disc cypselae angular, 2.5–3.5 mm, appressed hairy, especially on angles; pappi of ca. 8–10 lanceolate-attenuate and shorter, blunt fimbriate scales ca. 1–2.5 mm (alternating). 2n = 10, 12.

Calycadenia pauciflora is a species of flowering plant in the family Asteraceae known by the common name smallflower western rosinweed. It is endemic to northern California, where it grows in the Coast Ranges north of the San Francisco Bay Area from Napa County to Tehama County, often on serpentine soils.

Calycadenia pauciflora is an annual herb producing a slender, crooked, branching stem coated with hairs, growing up to 50 centimeters (20 inches) tall. The leaves are linear in shape and up to 5 centimeters (2 inches) long. The inflorescence bears bracts studded with large resin glands and small clusters of flower heads. The hairy, glandular flower head has a center of a few disc florets and one or two white or red triple-lobed ray florets. Each ray floret has three lobes at the tip, the middle lobe being shortest. The fruit is an achene; those developing from the disc florets have a pappus of scales.

Calycadenia pauciflora là một loài thực vật có hoa trong họ Cúc. Loài này được A.Gray mô tả khoa học đầu tiên.