Vachellia melanoceras (Beurl.) Seigler & Ebinger

Acacia melanoceras Buerling

Acacia melanoceras Buerling, 1854:362.

Acacia multiglandulosa Schenck, 1913:362.

Myrmecodendron melanoceras (Buerling) Britton and Rose, 1928:93.

Acacia melanoceras is easily recognized since it is the only swollen-thorn acacia in the wet lowlands of central Panama and the Canal Zone (Figure 29). Where its distribution is tangent with that of A. collinsii, about halfway through the Canal Zone, A. melanoceras is easily distinguished from that dry-forest species since A. melanoceras has a very large number of nectaries on the leaf petiole, longitudinally ridged swollen thorns, spherical inflorescences, and huge leaves.

I have been unable to locate the type specimen of A. melanoceras and it is likely destroyed; however, the type specimen of A. multiglandulosa (at Berlin, now destroyed, but represented by Field Museum photo 1281 ex Berlin) is from the same locality as that of A. melanoceras (site 1) and is probably described from the same specimen or a duplicate specimen of the same collection. The description of the type of both A. melanoceras and A. multiglandulosa agrees completely with the characteristics of the swollen-thorn acacia population whose distribution is plotted in Figure 29. The type specimen of A. multiglandulosa is a representative

distal end of a fertile branch from an adult acacia. Very long (20 cm) inflorescence-bearing branchlets such as the one on the type of A. multiglandulosa are commonly seen on old trees growing along river edges that have their crowns partly shaded by taller trees. The absence of swollen thorns on a branch bearing sexual branchlets, as is the case with the type specimen, is commonplace in old crowns of A. melanoceras. In 1915, Safford redescribed A. melanoceras, but under the name of A. multiglandulosa.

KEY COLLECTION LOCALITIES

1. Types of A. melanoceras and A. multiglandulosa: Portobello (Porto Bello), Colon, Panama (sea level). 1824, J.G. Billberg, no. 289.

2. Head of Gatun Valley, Canal Zone, Panama. 1914, H. Pittier, no. 6745 (US 716562, US 716560, US 716561; Safford 1915, Wheeler 1942).

3. Headwaters Rio Agua Salud, Canal Zone, Panama. Wheeler, III–6–1923 (Wheeler, 1942).

4. Marajal, near Colon, Canal Zone, Panama. Wheeler, VII–26–1924 (Wheeler, 1942).

5. Cerro Jefe, several mi N Cerro Azul, Panama, Panama. R.D. Dressier, VIII–28–1967 (pers. comm. plus thorn sample).

6. 400 m upriver (east bank) from the bridge at Rio Piedras, Colon. Panama. VII–3–1967, DHJ, nos. 1641, 1912, 1913, 1915, 1916, gp, mp.

7. Southwest corner of Zorro Island (in Gatun Lake), 5 km NW Nueva Providencia, Canal Zone, Panama. VII–7–1967, DHJ, no. 1894, gp.

8. 10 m post on Al. Ar. Trail, Barro Colorado Island, Gatun Lake, Canal Zone, Panama. DHJ, VII–7–1967, nc (I am indebted to R.D. Dressier for showing me this plant).

9. 7 km SW Gatun Locks on road to Escobal, Canal Zone, Panama. DHJ, VII–10–1967, nc (I am indebted to M. Nauman for showing me these plants).

Acacia melanoceras é uma espécie de leguminosa do gênero Acacia, pertencente à família Fabaceae.