Type: Foliicolous algae; Description: Thallus polystromatic, whitish, subcuticular at first, later penetrating the mesophyll, growing in intercellular spaces and filling substomatal chambers, composed of irregularly branched prostrate filaments; on the lower surfaces of leaves. Sporangiophores erect, 5–10 cells long, developing from filaments in the substomatal chamber and emerging through the stoma in tufts. Sporangia (1–several) borne laterally on short, curved stalks, produced on one side of the sporangiophore only, globose, 15–17 μm in diameter, smooth. Zoospores biflagellate. Gametangia sessile, produced on subepidermal filaments. Leaf spots on the upper surface stellate, pale lavender to deep rose, necrotic and sunken in the centre with a deep violet margin, 1–5 mm in diameter; on the lower surface <0.5 mm in diameter, whitish at the centre (due to tufts of sporangiophores) with a yellowish to reddish halo.

Distribution: Auckland, Bay of Plenty.; 1st Record: Chapman et al. (1957).

Significance: This alga causes an important disease of Theobroma cacao (cocoa) but is of no significance in New Zealand.; Host(s): Coprosma grandifolia, C. lucida, Knightia excelsa.