Endoraecium tropicum McTaggart & R.G. Shivas
Uredinia on both phyllode surfaces, subepidermal, pulverulent,
up to 2 mm, brown.
Urediniospores ovoid to fusiform, apex obtuse, yellowish brown, 30‒40 × 17‒22 μm; wall 3‒4 μm thick at sides, apex usually 3‒4 μm thick, sometimes slightly thickened (4‒5 μm), reticulate, with 3‒4, equatorial germ pores; pedicel 3‒4 μm.
Telia formed from uredinia, erumpent.
Teliospores clavate, apex rounded, papillate rather than digitate, 40‒53 × 16‒23 μm; wall 1.5‒2.0 μm thick at sides, 8‒11 μm thick at apex; pedicel persistent, 5 μm.
Endoraecium tropicum was closely related to E. parvum in phylogenetic analysis by McTaggart et al. (2015). Both species have urediniospores
with uniformly thickened spore walls. The distribution
of A. tropica is restricted to the Northern Territory and north-west Queensland. Acacia leiocalyx, the host of E. parvum,
occurs in eastern Australia (Maslin 2013).