Host: Scirpus inundatus Poir. On stems. Herb. Nos. 282, 325. Seashore (Wellington), E. H. Atkinson! 17 April, 1920; 27 Jan., 1921. Bog, Tiritea, Palmerston North (Wellington), 300 m., G. H. C. 4 March, 1921. Seashore, Bluff (Southland) W. D. Reid ! 26 May, 1922.

II. Uredosori caulicolous, scattered or crowded, elliptical, up to 2 mm. long, cinnamon-brown, bullate, pulverulent, becoming exposed by the longitudinal fissuring of the epidermis. Spores elliptical, obovate, or subglobose, 25-35 X 20-25 mmm.; epispore tinted cinnamon-brown, coarsely and sparsely echinulate, 2-2.5 mmm. thick, cell-contents granular, cinnamon-brown; germ-pores equatorial, 2, conspicuous.

Distribution: Victoria.

The host is indigenous, and is widespread, occurring in marshy localities from sea-level to 1,000m.; it occurs also in Australia, Malay Archipelago, and temperate South America. (Cheeseman, 1906, p. 775.)
The rust forms conspicuous bullate sori on the stems; these are usually severely infected with Darluca filum Cast. Characterized by the thick coloured epispore, and the two equatorial conspicuous germ-pores.

All host species [Scirpus spp.] are indigenous to New Zealand and occur throughout the country: the rust has been collected only in the Wellington and Nelson Provinces.

South Island, Otago Lakes, Cardrona Ski Field, on I. subtilissima Boeck., February 5, 1998, E.H.C. McKenzie (PDD 87918 – II, III).

Uredinia amphigenous, cinnamon brown, bullate, pulverulent, elliptical, up to 2 cm long. Urediniospores 23–29 × (16–)18–21(–23) µm (mean of 44 spores, 25.7 × 19.6 µm), obovoid to subglobose, contents very pale golden brown; wall 1.5–3 µm thick, pale golden brown, echinulate, germ pores 2, equatorial. Telia arising from same sori as the uredinia. Teliospores 27–41 × 10–17 µm (mean of 20 spores, 32.4 × 14 µm), ellipsoid or subclavate, straight or slightly curved, apex rounded or sometimes acuminate, constricted at the septum, contents very pale luteus, wall ca. 1 µm thick at sides, 1–4 µm at apex, smooth, pale luteus; pedicels up to 15 µm long, but usually broken shorter, 5–9 µm wide, hyaline.

Uredinia amphigena, cinnamomeo-brunnea, bulliformia, pulverulentia, elliptica, usque ad 2 cm longa. Urediniosporae 23–29 × (16–)18–21(–23) µm, obovoideae vel subglobosae, valde pallide aureo-brunnea, membrana 1.5–3 µm crassa pallide aureo-brunnea echinulata, poris germinationis 2 aequatorialibus. Telia uredinii similia, ex ipsis soris orientia. Teliosporae 27–41 × 10–17 µm, ellipsoidae vel subclavatae, ad septum constrictae, valde pallide luteae, membrana ad latera ca. 1 µm ad apicem 1–4 µm crassa levi pallide lutea, pedicello usque ad 15 × 5–9 µm pallide flavido.

Notes: This is the first record of a rust fungus on either Isolepis habra or I. subtilissima. McAlpine (1906) described Uredo scirpi-nodosi on Scirpus nodosus (= Ficinia nodosa (Rottb.) Goetgh., Muasya & D.A. Simpson; syn. Isolepis nodosa (Rottb.) R. Br.) from Victoria, Australia. He described the urediniospores as “brown, subglobose, ellipsoid to oblong, variable in size, 25–32 µ diam., or 27–36 × 19–25 µ; epispore echinulate, often 3 µ thick.” The species was subsequently reported from New Zealand (Cunningham 1924) and the urediniospores are described by Cunningham (1931) as “elliptical, obovate or subglobose, 24–35 × 16–24 µ, average 27 × 20 µ; epispore tinted cinnamon brown, coarsely and sparsely echinulate, 1.5 µ thick.” Cunningham (1924) stated that the epispore was 2–2.5 µm thick.
Further specimens of Uredo scirpi-nodosi in Herb. PDD were examined: PDD 61891 on Isolepis distigmatosa (C.B. Clarke) Edgar, PDD 34174 and 45171 on I. inundata R. Br., PDD 44048 on Ficinia nodosa, PDD 31479 and 41097 on I. prolifera (Rottb.) R. Br. These specimens had urediniospores measuring (23–)25–31(–35) × (16.5–)19–26(–28) µm (mean 120 spores, 27.8 × 22.6 µm). U scirpi-nodosi has been also recorded on Bolboschoenus medianus (V.J. Cook) Soják and Schoenoplectus tabernaemontani (C.C. Gmel.) Palla (= S. validus (Vahl) Á. Löve & D. Löve) in New Zealand (McKenzie 1998).
Gjærum (1990) described Puccinia isolepidis on Isolepis fluitans from Ethiopia. This rust has urediniospores that measure 21–27 × 13–21 µm, which is smaller than those described for Uredo scirpi-nodosi (McAlpine 1906). In addition, the urediniospore wall is only 1(–1.5) µm thick in P. isolepidis, compared to up to 3 µm in U. scirpi-nodosi. The teliospores of P. isolepidis are considerably larger than those of P. austrina (38–65 × 16–24 µm vs. 27–41 × 10–17 µm).

Campbell Island, Mt. Honey, on Isolepis habra (Edgar) Soják [Cyperaceae], March 7, 2000, E.H.C. McKenzie (PDD 87917 – II, III – HOLOTYPE)