The overall peculiarities of pernambuco wood are easily recognized and with a little effort, the species can be identified in the wild (figures 6, 7, 8). It is usually a medium-sized tree, but may grow to 20 meters. Stem diameter frequently varies from 30 to 40 cm, but surpasses 70 cm in the larger trees. The irregular trunk tends to branch early on, and rarely surpasses 5 meters in height. Its irregular base has small incurvations and excurvations. The dark gray bark is rather thin, with irregular patches which loosen and fall, exposing a reddish brown surface. In the young trees the bark has strong, rather indistinct prickles, which are slightly elongated and provided with a small, curved, pointed tip not over 1 cm long. The wood is very hard and compact. The heartwood varies in color from bright orange to reddish brown, turning darker when cut. The sapwood is sharply defined, consisting of a narrow, whitish or yellowish strip.
The tree crown is usually quite irregular, or sometimes becomes almost circular, with most branches reaching upward. These branches have light gray older sections and dark green tips. Prickles are usually present in the younger branches. The leaves are attached alternately along the branches; they are compound and bippinate, with 6 to 11 pinnas and 8 to 21 leaflets per pinna. The rachis is often aculeate and the leaflets oblong-trapezilform, dark green and shiny.
The pleasantly sweet-smelling flowers are clustered in small, terminal (rarely axillary) racemes or panicles. The calyx is yellowish-green and the corolla has yellow petals, the middle one with a dark red splotch in the center. The androecium has 10 distinct, unequal stamens; the yellowish white gynecium is rather hairy.
The fruits are elliptical, oblong-elliptical or sometimes slightly wider at the apex; they are 6 to 8 cm long and 2 to 3 cm wide. The valves are aculeate on the outside; after dehiscence they become curved or twisted. The chestnut-colored seeds, 1 to 1.5 cm in diameter, are flattened and irregularly spherical.
Although only one species of pernambuco wood is recognized today, leaflet shape and size vary considerably within the species. Several populations, which present marked differences in these characteristics, are under study, including wood anatomy wherever possible. This analysis will most likely show the need to separate subspecies or varieties within C. echinata.
Three morphological distinct groups have been detected up to now. The most common variant has been observed at several locations along the Brazilian coast. It has smaller leaflets (figure 7a) and the wood is often an orangy-chestnut color. The second variant differs slightly from the first in its larger leaflets and reddish-orange wood (figure 7b). Individuals with these characteristics were observed only in cultivation at the Sooretama Biological Reserve (Espirito Santo) and Rio de Janeiro Botanical Garden. The third variant has large leaflets (figure 7c) up to 12 cm long and blackish-red wood. Several individuals with these marked differences were found in Bahia. Young specimens from this population are under cultivation at the Rio de Janeiro Botanical Garden.