Type: Powdery Mildews; Description: Mycelium superficial, thin, white, hyphae 4–5 μm wide; on leaves, twigs, and inflorescences. Appressoria multi-lobed. Ascomata cleistothecial, densely gregarious, superficial, depressed globose, brown, 0.1–0.2 mm in diameter, with numerous 200–800 μm long, rarely branched, hyaline appendages. Asci 6–22 per ascoma, saccate to oblong oval, 60–85 × 25–35 μm. Ascospores 8 per ascus, ellipsoid, 0-septate, 18–20 × 9–12 μm, smooth, hyaline. Conidiophores 94–130 × 7–9 μm, foot cell flexuous. Conidia produced singly, cylindrical-ovoid, 0-septate, 25–50 × 13–17 μm, smooth, hyaline.

Distribution: Auckland.; 1st Record: Sydow (1924).

Significance: None.; Host(s): Weinmannia racemosa, *W. sylvicola.

Mycelium persistens vel hinc inde evanescens, album; perithecia plus minus dense gregaria, globoso-depressa, 140-200 µ diam., cellulis ca. 10 µ diam.; appendices numerosae, dense intricatae, bis usque quater perithecii diametrum longitudine attingentes, hyalinae, 3--4 ¹/2 µ latae, simplices vel parum ramosae; asci 6-20 in quoque perithecio, saccati vel ovato-oblongi, 60-85 x 25-35 µ, 6-8-spori, plerumque 8-spori; sporae maturae jam in planta viva evolutae, continuae, ellipsoideae vel oblongo-ellipsoideae, hyalinae, 18-20 x 9-12 µ.

Die Art steht der Erysiphe aggregata (Peck) Parl. sehr nahe und unterscheidet sich namentlich durch kleinere, weniger zahlreich entwickelte Schläuche. Da jedoch die genannte Art bisher ausschlielich auf Alnus- Kätzchen in Nordamerika gefunden wurde, so stellt der neuseeländische Pilz zweifellos eine eigene Art dar. An dem uns vorliegenden Exemplare ist der Pilz ausschlielich an den Samenschalen entwickelt, die dicht mit dem weilichen Myzel überzogen sind und zahlreiche Fruchtkörper aufweisen. Die mitgesammelten unmittelbar unter dem Fruchtstand befindlichen Blätter sind vollig pilzfrei, so da sich die neue Art anscheinend nur an den Kapsein entwickelt.

Hab. in capsulis Weinmanniae sylvicolae, Auckland, 19. 1. 1923, leg. A. G. Elliot (no. 943)

Within this herbaceous host group, four species collected in the southern hemisphere (viz. E. balbisiae, E. acaenae, E. frickii, E. carpophilla) grouped into a clade. Erysiphe acaenae, E. frickii and Erysiphe sp. on Potentilla collected in Argentina had identical rDNA sequences, although they were described as different species and infect different plant genera in the Rosaceae. In addition, a sequence deposited in DNA databases as E. carpophila on Weinmannia silvicola from New Zealand also has an ITS sequence identical to the above sequences. Weinmannia silvicola is a woody plant, a native of New Zealand belonging to the Cunoniaceae. It is curious that this fungus has a sequence identical to the fungi on rosaceous hosts from South America.