Conzattia Rose, Contrib. U.S. Natl. Herb. 12(9): 407. 1909.

Figs 67, 68, 70, 74

Type.

Conzattia arborea Rose [= Conzattia multiflora (B.L. Rob.) Standl.]

Description.

Unarmed, small to medium-sized tree, 3-10 (15) m, generally forking low down with a large spreading flat-topped ‘umbrella’ crown (Fig. 67L), the trunk 20-50 (75) cm in diameter, the bark thin, pale silver-grey (Fig. 67M), inner bark green, whole plant largely glabrous. Stipules minute. Leaves bipinnate, with 10-15 pairs of pinnae, 9-20 pairs of leaflets per pinna, leaflets oblong, apex acute, oblique at base. Inflorescences slender, erect, 6-12 (25) cm long axillary racemes clustered near branch tips, pedicels jointed just below the flower; bracts caducous. Flowers unisexual by reduction of the androecium or gynoecium, usually dioecious but some individuals carry both functionally male and female flowers; hypanthium shallowly campanulate; sepals 5, free, imbricate only in bud, strongly reflexed, subequal; petals 5, yellow, more or less equal (Fig. 68F); stamens 10, free, slightly shorter than petals, anthers dorsifixed, glabrous; pollen in oblate tricolporate monads with moderately reticulate surface ornamentation; ovary densely pubescent, stipitate, 6-ovuled (ovaries of functionally male flowers smaller, not fully developed), style filiform, usually straight in functionally female flowers, swan-necked in functionally male flowers, stigma ciliate. Fruits plano-compressed, glabrous, the margins narrowly winged, acuminate at apex, dehiscent along both sutures, (2) 3 (4)-seeded (Fig. 70J). Seeds oblong, 10-12 mm long, brown, albuminous.

Chromosome number.

Unknown.

Included species and geographic distribution.

Monospecific, endemic to seasonally dry western and southern Mexico from Sonora and Baja California Sur south to Chiapas (Fig. 74).

Ecology.

Confined to seasonally dry tropical forest. Strongly deciduous, fruits ripening when leafless (Fig. 67L), and flowering preceding leaf flush.

Etymology.

Named in honour of the Italian-born Mexican botanist Cassiano Conzatti (1862-1951), a prodigious plant collector in Mexico and Chile and director of the Escuela Normal in Oaxaca, Mexico.

Human uses.

Conzattia has been listed as an important source of medicine and wood for construction and fuel, and immature fruits are used as a Hoffmannseggia minor food in Mexico (Arellano 1987). The presence of seeds of Conzattia multiflora at several archaeological sites in south-central Mexico and the frequent occurrence of trees around pre-Colombian temple sites suggest use as a Hoffmannseggia minor food spanning several millennia ( Zárate 2000).

Notes.

Conzattia is robustly supported as sister to Heteroflorum (Fig. 66; Haston et al. 2005; Ringelberg et al. 2022), both genera endemic to Mexico and sharing seasonally dry tropical ecology, and both with similar low, flat-topped tree crowns (Fig. 67J, L), smooth grey bark (Fig. 67K, M), yellow flowers and frequently at least partial dioecy, but readily distinguished by their radically different fruits (Fig. 70J-M). Three species of Conzattia have been described based on Hoffmannseggia minor differences in leaf indumentum, quantitative variation in leaf formula and stipules, none of which are fixed or correlated with geography, prompting recognition of a single somewhat variable species C. multiflora (Haston 2003).

Taxonomic references.

Haston (2003); Lewis (2005b) with illustration; Standley (1922).