Pericladium grewiae Pass.


Ustilago grewiae (Pass.) Henn.


Sori on stems, forming globose pustular bodies c. 1–2 mm diam., gregarious to crowded, sometimes entirely surrounding the stems, covered by a brown coriaceous peridium composed of host tissue and fungal elements. At maturity, the peridium ruptures irregularly revealing the central mass of black semi-agglutinated spores.

Spores at first agglutinated in irregular groups, later solitary, ±flattened on one side, flattened-hemiglobose, with a convex side and an opposite flat side, (5.0–) 5.5–7.0 µm wide, in face view rounded to elliptical, 7.0–10.5 × 7.0–8.5 µm; wall chestnut-brown, c. 1 µm thick; flattened side pale yellowish brown, c. 0.2 µm thick, smooth.

Spore germination resulting in an ovoid basidium 10–15 × 6–9 µm, with 8–12 nuclei. From the basidium branched septate hyphae arise on which secondary ovoid sporidia develop, 5.5–8.0 × 3.0–5.5 µm. Septate branched 2.5–3.5 µm thick hyphae sometimes arising directly from the spores, similar to those resulting from germinated basidia.

Host family: Tiliaceae
Host species: Grewia breviflora Benth.
Grewia retusifolia Kurz


States & Territories: NT, QLD, WA