4. Tilletia Holci (Westendorp) Rostrup. (Text-fig. 16.) Rostr., Ust. Daniae, p. 156, 1890. Polycystis Holci Westnd., Bull. Acad. Belg., ser. 2, vol. 11, p. 660, 1860. Tilletia Rauwenhoffii F. v. Waldh., Apercu Syst. Ust., p. 50, 1877. Sori in ovaries, partially concealed within the glumes, elliptical, 1–2 mm. long, compact, black, slightly fetid. Spores globose or subglobose, 22–32 × 24–28 mmm.; epispore covered with a network of raised reticulations 3–4.5 mmm. high, surrounding polygonal depressions 4–7 mmm. wide, chestnut-brown. Host: Holcus lanatus L. In inflorescences. Herb. No. 500. Ettrick (Otago), 300 m., R. B. Tennent! 10 Feb., 1921. Distribution: Europe; North America. I have a collection of Holcus lanatus L. with this species in the ovaries and Ustilago striaeformis in the leaves. The three species possessing reticulate spores may readily be separated if the following differences are noted:— Spores under 25 mmm. T. Tritici. Spores over 25 mmm.   Reticulations 2–2.5 mmm. high T. decipiens.   Reticulations 3–4.5 mmm. high T. Holci. Furthermore, the reticulations of T. Holci are coarse, and separated by large polygonal interspaces; those of T. decipiens are closely compacted, being separated by much smaller areas; whilst those of T. Tritici are intermediate in size. I have been unable to germinate the spores of T. Holci. 6. Sorosporium Rudolphi. Rud., Linnaea, vol. 4, p. 116, 1829. Sori in the form of dark-coloured pulverulent spore-masses in various parts of the host, chiefly in the inflorescences, formed of numerous spore-balls, consisting of few or many spores, at first somewhat loosely united, but at maturity completely separating; sterile cells absent. Spores coloured some shade of brown, globose to angular, smooth or verruculose; germination similar to that of Ustilago. Distribution: World-wide. New Zealand species two—one endemic, the other indigenous; both are confined to the Cyperaceae. Members of the genus have elsewhere been recorded on the following families: Gramineae, Cyperaceae, Juncaceae, Portulaceae, and Caryophyllaceae. McAlpine (1910) records thirteen species for Australia. The genus is characterized by the rather temporary nature of the spore-balls, for these generally break up at maturity, when species cannot be distinguished from Ustilago. In one or two species the balls remain somewhat firmly united, when they are liable to be confused with the allied genera Thecaphora and Tolyposporium. The former may be separated by the pallid colour of the spore-balls, and the fact that the spores are variously marked on their free, but smooth on their united surfaces (seen when the spores are separated), the latter by the individual spores being firmly united in the ball by ridged folds of their epispores. Spore-formation has been investigated by Fischer von Waldheim (1869) in the type species, S. Saponariae Rud. The mycelium in the infected region