Atkinson E. H. (1921) noted that a Heterosporium sp. was associated with small purple blotches on leaves [of Phormium tenax], predominantly on the under surfaces of leaves: he noted that this fungus did not appear to affect the quality of the fibre in the leaf. Ellis (1967) described this fungus as Periconiella phormii.

Colonies hypophyllous, grey to dark blackish brown, hairy. Mycelium partly superficial, partly immersed in the substratum, the two parts linked by thick brown hyphae passing through the stomata. Superficial hyphae branched, septate, for the most part pale olivaceous brown, verruculose and 1-3 µ thick, below conidiophores usually swollen to 4-6 µ, smooth and brown. Immersed hyphae colourless, smooth, 1-4 µ thick. Conidiophores arising singly or in groups, terminally and laterally on the hyphae, simple or with one branch. Stipes erect, straight or flexuous, cylindrical or subulate, septate, brown, paler towards the apex, smooth, up to 260 µ long, 3-5 µ thick. Branches simple, cylindrical, with numerous conidial scars, up to 60 µ long, 3-5 µ thick. Conidia acropleurogenous, solitary, cylindrical, rounded at the apex, truncate at the base, 0-3-septate, pale olivaceous brown, verruculose, 12-27 (21) µ, long, 3-3-5 (32) µ, thick.

Coloniae hypophyllae, griseae vel fuscae, pilosae. Mycelium partim superficiale, partim in substrato immersum. Hyphae superficiales ramosae, septatae, pallide olivaceo-brunneae, verruculosae et 1-3 µ crassae, sub conidiophoris ad 4-6 µ. inflatae, leves et brunneae. Hyphae immersae incoloratae, leves, 1-4 µ crassae. Conidiophora singula vetl fasciculata ex apice lateribusque hypharum oriunda, simplicia vel ramo uno praedita. Stipites erecti, recti vel flexuosi, cylindrici vel subulati, septati, brunnei, apicem versus pallidiores, leves, usque ad 260 µ longi, 3-5 µ crassi. Rami simplices, cylindrici, pallide brunnei, cicatricibus conidialibus numerosis ornati, usque ad 60 µ longi, 3-5 µ crassi. Conidia acropleurogena, solitaria, cylindrca, apice rotundata, basi truncata, 0-3-septata, pallide olivaceo-brunnea, verruculosa, 12-27 (21) µ longa, 3-3.5 (3.2) µ crassa.

On living leaves of Phormium tenax, New Zealand, causing large, reddish purple blotches on the lower surface of the leaves. This appears to be the fungus referred to as Heterosporium sp. by E. H. Atkinson in N.Z. fl. Agric., 23: 298-302, 1921 and Bull. N.Z. Dep. Agric., 95 (N.S.): 46, 1922.

Habitat in foliis vivis Phormii tenacis, Papiatonga Reserve, Levin, New Zealand, A. Ward, 31.V.1966, IMI 123224 typus

Type: Foliicolous Fungi; Description: Mycelium both internal and external. Hyphae of internal mycelium smooth, hyaline, 1–4 im wide, connected with the external mycelium by thick brown hyphae passing through stomata; hyphae of external mycelium pale olivaceous brown, verruculose, 1–3 hm wide. Conidiophores single or in small groups, arising from the external mycelium, simple or with one branch, erect, straight or flexuous, brown, smooth, up to 260 sm long, with numerous conidial scars towards the apex. Conidia cylindrical, 0–3-septate, 12–27 × 3–4 m, verruculose, pale olivaceous brown, base truncate. Leaf spots irregular, reddish purple, the external mycelium being visible as a blackish brown hairy colony on the lower surfaces of leaves.

Distribution: Auckland, Bay of Plenty, Wanganui, Wellington, Westland.; 1st Record: Kirk & Cockayne (1909: as Cladosporium sp.).

Significance: Atkinson (1921) noted the reddish brown blotches on flax leaves and stated that fibre quality was not affected by fungal infection.; Host(s): Phormium cookianum, P. tenax.

[Notes from Kew Type specimen, PRJ 2010] Kew images.