Circaea L., 1753

Luo, Yike & Xie, Lei, 2023, A checklist of Onagraceae in the Pan-Himalaya region, Phytotaxa 597 (4), pp. 245-268 : 250

2. Circaea L.

Lectotype (designated by Britton & Brown 1913):— Circaea lutetiana Linnaeus (1753: 9) .

Erect perennial herbs. Stems usually cespitose. Leaves opposite and decussate, with long petiolate. Inflorescence simple or branched racemes. Flowers 2-merous; floral tube, ca. 2.4 mm long; ovary unilocular or bilocular, 1 seed per locule; petal 2, alternate, white or pink, notched at the apex; stamens 2, opposite the sepals; filaments as same color as the petals; nectary completely within and filling the lower part of the floral tube, or elongated and protrude above the opening of the floral tube as a disc. Indehiscent capsule covered with uncinate hairs. Seed smooth, firmly inset to the inner ovary wall. Chromosome number, n = 11 ( Boufford 1982).

Circaea comprises eight species (14 taxa) ( Boufford 1982), and six species (eight taxa including subspecies) in the Pan-Himalaya region. The genus is distinctive with other genera in Onagraceae by having 2-merous flowers and indehiscent fruits covered with hooked hairs ( Boufford et al. 1990). The sister relationship between Fuchsia Linnaeus (1753: 1191) and Circaea has been confirmed by molecular phylogenetic studies ( Berry et al. 2004, Wagner et al. 2007, Xie et al. 2009).

Key to species of Circaea in the Pan-Himalaya region

1 Ovaries and fruits unilocular; rhizomes terminated by tubers............................................................................................................2

- Ovaries and fruits bilocular; rhizomes without tubers .......................................................................................................................3

2 Apical notch 1/2 or more length of petal; pedicels glandular pubescent; leaves with 9–15 secondary veins; combined length of mature fruit and pedicel 7.5–15 mm .............................................................................................................................. 2.6. C. repens

- Apical notch 1/2 or less length of petal; pedicels glabrous; leaves with 4–10 secondary veins; combined length of mature fruit and pedicel 3.5–7.8 mm ........................................................................................................................................................2.1. C. alpina

3 Nectary wholly included within the floral tube..................................................................................................................................4

- Nectary exserted beyond the floral tube.............................................................................................................................................5

4 Axis of inflorescence with glandular and nonglandular hairs.......................................................................................2.2. C. cordata

- Axis of inflorescence glabrous or with only glandular hairs................................................................................. 2.4. C. glabrescens

5 Stem glabrous; petal apical notch to more than 1/10–1/5 their length ................................................................... 2.3. C. erubescens

- Stem pubescent with falcately recurved hairs; petal apical notch to more than 1/4–1/2 their length ............................ 2.5. C. mollis