Bunchosia sect. Coelostylis Adr. Juss., Ann. Sci. Nat. Bot., Sér. 2, 13: 325. 1840. Coelostylis (Adr. Juss.) Kuntze, Rev. Gen. Pl. 1: 87. 1891, non Coelostylis Torr. & A. Gray ex Endl., 1839.—Type: B. eglandulosa Adr. Juss. [Echinopterys eglandulosa (Adr. Juss.) Small].
Shrubs or woody vines, occasionally described as small trees; vegetative hairs medifixed; leaves alternate or alternate and opposite, rarely all or most opposite, eglandular. Inflorescence terminating a leafy stem; pedicels pedunculate; floriferous bracts and bracteoles eglandular, persistent. Sepals leaving outermost petals exposed in enlarging bud, eglandular; corolla bilaterally symmetrical, the posterior petal with a thicker claw and a more erect stance; petals abaxially moderately to densely sericeous or appressed-tomentose on claw and in center of limb, adaxially glabrous, erose or denticulate; androecium radially symmetrical, the stamens alike, densely appressed-tomentose or tomentose on both filaments and anthers; filaments connate at base; pollen with 6–12 very short colpi, "equatorial to sub-equatorial," and 6 or more pores, "usually at or towards the end of a colpus, rarely independent of the colpi" (Lowrie, 1982); gynoecium bilaterally symmetrical, the carpels 3; styles 3, distinct for proximal 2/3 or more of their length but coherent distally in stigmas or below distinct stigmas, the cluster of styles curved toward posterior petal; stigmas apical and capitate, coherent or distinct. Fruit dry, apparently indehiscent or only very tardily schizocarpic (E. eglandulosa) or soon breaking apart into 3 mericarps separating from a short pyramidal torus (E. setosa); mericarp covered on back and sides with many long, slender, vascularized setae arrayed in several roughly vertical rows but giving the impression of completely covering abaxial surface of nut. Chromosome numbers: n = 10, 20 (W. R. Anderson, 1993a).
Two disjunct species, found only in seasonally dry habitats in Mexico. [map]
Among Mexican Malpighiaceae this genus is easy to recognize, through the combination of the eglandular leaves and sepals with the leaves often alternate, the hairy bright yellow petals and hairy stamens, the coherent styles, and the bristly fruits. Its elongated pseudoraceme immediately distinguishes it from the only other Mexican genus with a bristly fruit, Lasiocarpus, which is not closely related to Echinopterys; Lasiocarpus belongs to the Ptilochaeta clade [family phylogenetic tree].
In the Bunchosia clade, the only other genus with a setiferous fruit is the Cuban endemic Henleophytum; see the discussion under that genus.
|1.||Petiole (2–) 3–9 mm long; lamina 4.5–30 mm wide, 1.4–3.3 times as long as wide; sepals erect in anthesis or somewhat revolute at apex; styles coherent below stigmas, the stigmas distinct; fruit indehiscent (?) or only belatedly dehiscent, the setae plumose with very short, spreading hairs; western and southern Mexico from Sonora to Oaxaca.|
E. eglandulosa (Adr. Juss.) Small
|1.||Petiole 0.5–1.5 (–2) mm long; lamina 1.5–3.5 mm wide, (3.3–) 4–6.7 times as long as wide; sepals strongly revolute in anthesis; styles coherent in stigmas; fruit soon breaking apart into 3 mericarps, the setae glabrous or only minutely scabrellous; Coahuila, Mexico.|
E. setosa Brandegee
Etymology: The name Echinopterys comes from the Greek words for hedgehog or sea-urchin (echinos) and wing (pteron), referring to the fact that instead of having the kind of undissected wing found in most Malpighiaceae with winged fruits the fruit of this genus is covered with many erect vascularized setae.
Drawings: E. eglandulosa, E. setosa