Carsonia

Herbs, annual. Stems profusely branched; glabrous. Leaves: stipules scalelike or absent; petiole with pulvinus basally or distally; leaflets 1 or 3. Inflorescences terminal or axillary (from distal leaves), racemes (flat-topped or elongated); bracts present. Flowers weakly zygomorphic; sepals deciduous, distinct, equal; petals equal (each with an epipetalous nectiferous scale); stamens 6; filaments inserted on 4-lobed androgynophore, glabrous; anthers (linear), coiling as pollen is released; gynophore erect in fruit. Fruits capsules, dehiscent, oblong. Seeds 10–13, oblong, not arillate, (cleft fused between ends). x = 16.

Distribution

sw United States.

Discussion

Species 1.

A peculiar desert xerophyte with subsessile, erect capsules, and unique petal glands, Carsonia is segregated from Peritoma by its unique cytology (2n = 32). Whether it is autochthonously specialized or actually related to, and derived from, some Old World ancestors, such as the Central Asiatic-Near Eastern Cleome sect. Thylacophora Franch, the dozen or so species of which, probably through convergence, also bear epipetaloid glands, remains to be determined.

Selected References

None.

Lower Taxa

Carsonia sparsifolia