XII. EBENOPSIS Britton & Rose
Ebenopsis Britton & Rose, N. Amer. Fl. 23: 33. 1928, a legitimate substitute for Siderocarpos Small, Bull. New York Bot. Gard. 2: 91. 1901; non Siderocarpus Pierre, 1890. — Sp. typica: Siderocarpos flexicaulis (Bentham) Small = Acacia flexicaulis Bentham = Ebenopsis flexicaulis (Bentham)
Britton & Rose = Ebenopsis ebano (Berlandier) Barneby & Grimes.
Ebenopsis sensu Mohlenbrock, 1963: 439.
Havardia sensu Nielsen in Polhill & Raven, 1981: 184, parva ex parte.
Chloroleucon sensu Rico, 1991: 519, parva ex parte.
Xeromorphic trees and shrubs with stiffly flexuous branches. Stipules associated with primary lvs subulate from swollen base, early lignescent, vulnerant, persistent. Lf-formula i-iv/2-7; lf-nectaries interpinnal, cupular short-stipitate; lfts opposite, of relatively broad outline, the primary venation palmate, the midrib often expiring short of blade-tip. Inflorescence of spikes or capitula arising from brachyblasts, the fls sessile; calyx 1-1.5 mm; corolla ±3-4.5 mm, the lobes erect; androecium 32-66-merous, the tube included or barely exserted, charged internally at base with small callosities sometimes cohering into a continuous lobed disc. Pods massive, compressed-sausagelike (reminiscent of Tamarindus), the woody valves produced inwardly as pithy interseminal septa, the exocarp in age breaking into polygons; dehiscence tardy, inert, the sutures at first separating at each end of pod but not gaping, ultimately separating through their whole length; seeds transverse on straight, subterete funicle, plumply obese, resembling chickpeas (but red-castaneous in color). — Spp. 3, of warm temperate and dry tropical Mexico and S Texas.
Exomorphic features shared by Ebenopsis with some or all species of Havardia and kindred genera are: dimorphic branches, the units of inflorescence arising from axillary brachyblasts along annotinous long-shoots; spinescent stipules; low leaf-formula; a nectarial disc or callosities around stipe of ovary. But the massive, ligneous, internally septate pod and the obese reddish seeds are unique. Although the pod in many specimens seems indehiscent, the valves do tardily separate, at first at each end of the fruit but finally throughout its length, into two canoe-shaped halves. The status of the group depends on subjective evaluation of carpological characters.
The transfer to Chloroleucon of Ebenopsis ebano, recently proposed by Rico (1991: 519), is summarily rejected. Rico speaks (1. c.) of Chloroleucon as one of three American pithecellobioid genera with spinescent stipules. This mistake, perhaps copied thoughtlessly from Nielsen (1981: 182), could have been avoided by paying attention, if not to specimens, to Bentham’s protologue of Pithecolobium sect. Chloroleucon, where the armament was correctly described as spinae . . . axillares. These axillary thorns are barren and indurated inflorescence axes, in no way homologous to the genuine indurated stipules of Ebenopsis or Havardia. The real stipules of Chloroleucon are submembranous, precocious, and evanescent, but when these are lacking the true nature of the thorns can be inferred from the supra-axillary insertion. The same misinterpretation of armament was made by Nielsen et al. (1983a: 323) in the case of Cathormion Hasskarl.
Cassens and Miller (1981) noted that the wood of Ebenopsis is distinguished by the color of the heart- wood and the high specific gravity.