4. Gyrandra Grisebach in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 9: 44. 1845.
Centaury [Greek gyros, circle, and andros, of male, alluding to helically twisting showy anthers at dehiscence]
James S. Pringle
Herbs perennial [annual], chlorophyllous, stems, leaves, and calyces scabridulous to papillate-puberulent in lines. Leaves basal and cauline, opposite. Inflorescences partly dichasial, partly monochasial [completely monochasial] cymes. Flowers 5-merous; calyx lobed nearly to base; corolla [pale violet to] deep rose-pink without distinct white eye, salverform [subrotate], glabrous, lobes abruptly spreading ± as long as [longer than] tube, margins entire, plicae between lobes absent, spurs absent; stamens inserted in distal 1/2 of corolla tube, all initially curved to one side; anthers distinct, coiling helically at dehiscence; ovary sessile; style deciduous, initially deflexed away from stamens, distinct, not cleft, not coiling; stigma 1, shallowly 2-lobed [subcapitate]; nectaries absent. Capsules ellipsoid. x = 18.
Species 6 (1 in the flora): Texas, Mexico, Central America; warm-temperate to dry-mesic tropical regions.
G. Mansion (2004) and Mansion and L. Struwe (2004) inferred from molecular studies that Gyrandra is more closely related to Eustoma and Sabatia than to Zeltnera, although it resembles Zeltnera in its helically coiling anthers and in its calyx with a short tube and strongly ascending lobes.
Gyrandra differs from most species of Zeltnera in having corolla lobes about as long as or longer than the tube. Some Mexican species of Gyrandra have large, nearly rotate corollas with the lobes two to three times as long as the tube. In G. blumbergiana and the Mexican G. brachycalyx (Standley & L. O. Williams) G. Mansion, however, the lobes are about as long as the tube; conversely, in Z. multicaulis, Z. trichantha, and Z. venusta the corolla lobes are occasionally as long as or longer than the tube.
Gyrandra further differs from Zeltnera in its abaxially viscid corolla tubes, best observed in fresh material [C. R. Broome 1973, as Centaurium sect. Gyrandra (Grisebach) A. Gray]. The capsule walls of all species of Gyrandra are relatively thick and woody at maturity, whereas those of Centaurium and Zeltnera are variable in this respect, often being very thin. The angles of the stems of Gyrandra are minutely serrulate or papillose, whereas the stems of all Zeltnera species except Z. glandulifera are smooth. The leaves of Gyrandra are generally linear to narrowly lanceolate, more or less densely crowded proximally but not forming a distinct rosette, gradually more widely spaced distally, all persistent at flowering time.
