Art. 44.—The Uredinales, or Rust-fungi, of New Zealand: Part I— Pucciniaceae, Tribe Puccineae (containing Descriptions and Illustrations of Seventy-five Species). By G. H. Cunningham. [Read before the Wellington Philosophical Society, 27th October, 1921; received by Editor 31st December, 1921; issued separately, 8th June, 1923.] Plate 77. Of the three classes into which the fungi are divided by systematists (if we exclude the Fungi Imperfecti) the third class, the Basidiomycetes, is characterized by the fact that the spores are borne at the apices of sterigmata which are in turn borne on basidia (see figs. 1, 2). Fig. 1.—Basidia of Agaricus arvensis : a, basidium; b, sterigma; c, basidiospore; d, paraphysis. × 500. Fig. 2.—Germinating mesospore of Puccinia novae-zelandiae n. sp.: a, basidium; b, sterigma; c, basidiospore; m, mesopore; p, pedicel. × 500. In this class are included the Uredinales, for the reason that the teleutospores (or final spores produced in the cycle of development) on germination produce basidia,* Basidium = promycelium. The former is the more suitable term. which become divided into four cells by cross-septa, each segment producing a sterigma on which a basidiospore† Basidiospore: In accordance with the classification this is the correct term to use. These spores are commonly termed “sporidia” or “sporidiola.” is borne (see fig. 2, c). Biology. All rusts are parasitic during their entire life-cycle, which consists of one or more spore-forms, occurring on the same (autoecious) or on different (heteroecious) host plants. The cycle is a complex one, and includes as many as five spore-forms. As a rule all species are highly specialized, and each can infect but one host plant; exceptions occur, however—e.g., Puccinia Malvacearum Bert., which attacks plants belonging to many different genera of the family Malvaceae.