Brachystigma

Herbs, perennial; hemiparasitic, caudex woody. Stems erect, not fleshy, hirsutulous. Leaves cauline, in whorls of 3; petiole absent; blade not fleshy, not leathery, margins entire. Inflorescences terminal, racemes; bracts present. Pedicels present; bracteoles absent. Flowers: sepals 5, calyx nearly radially symmetric, broadly campanulate, lobes deltate; petals 5, corolla yellow, bilabiate, subrotate, abaxial lobes 3, adaxial 2; stamens 4, didynamous, filaments glabrescent proximally, villous distally; staminode 0; ovary 2-locular, placentation axile; stigma clavate. Capsules: dehiscence loculicidal. Seeds 100+, dark brown, ellipsoid, wings absent or present.

Distribution

sw United States, n Mexico.

Discussion

Species 1.

Brachystigma is monospecific and narrowly restricted to dry mountain slopes of southeastern Arizona, southwestern New Mexico, and northern Mexico. F. W. Pennell (1928) differentiated it from the similar genus Agalinis by its yellow corollas, glabrous anthers, capitate stigmas, more acute capsules, and winged seeds. Phylogenetic analysis of three chloroplast genes supports this distinction (M. C. Neel and M. P. Cummings 2004). Further, Brachystigma may be differentiated from closely related genera Aureolaria, Dasistoma, and Seymeria by its leaves arranged in whorls of three, a characteristic unique in Orobanchaceae.

Selected References

Pennell, F. W. 1928. Agalinis and allies in North America: I. Proc. Acad. Nat. Sci. Philadelphia 80: 339–449.

Lower Taxa

Brachystigma wrightii