A Revision of the New Zealand Nidulariales, or “Birds-nest Fungi.” By G. H. Cunningham, Mycologist, Biological Laboratory, Wellington, N.Z. [Read before the Wellington Philosophical Society, 23rd October, 1922; received by Editor, 31st December, 1922; iussed separately, 26th May 1924.] Plates 3, 4. All species belonging to this order are saprophytic, occurring on decaying wood, old sacking, or on the ground. They favour moist localities, and may commonly be found growing on humus on the forest-floor. The fructifications are quite small, seldom attaining a greater diameter than 10 mm.; they may be cup- or funnel-shaped, although frequently obconic forms occur. The order is widely distributed, and some of the species have been found in nearly every country in the world; others, again, have a very limited distribution, occurring in but one or two localities. The order comprises only one family, the Nidulariaceae, consisting of the four genera Cyathus, Crucibulum, Nidula, and Nidularia. The genus Sphaerobolus, at one time included in the Nidulariaceae, was by Ed. Fischer (1900, p. 346) placed in a separate family, the Sphaerobolaceae. In structure the fructifications of all genera, mutatis mutandis, are essentially alike, a typical fructification consisting of a peridium containing numerous lenticular bodies, peridiola (also termed “sporangioles”), which in turn enclose the hymenium, consisting of basidia and paraphyses. The peridium is typically campanulate, although obconic or infundibular forms occur. It consists of a single thick felt-like layer of closely woven hyphal filaments (in Cyathus it is composed of three layers). The apex is at first enclosed by a thin epiphragm (absent in Nidularia, the peridia of which are globose, and at maturity dehisce by the irregular rupture of the walls), which at maturity becomes ruptured and finally gelatinized. This membrane, in Crucibulum, is formed of the same tissue as the peridium, but in Cyathus is composed of the ungelatinized portion of the gleba, which at first is covered by the peridium; during development the peridial wall gradually becomes pulled away and the uppermost portion becomes exposed, appearing as a thin white membrane. The peridiola are lenticular in shape, and in structure consist of an outer loosely woven covering of hyphae, the tunica (which in certain species of Cyathus may be very thin or wanting), enclosing a partly gelatinized layer, the cortex. This structure is closely compacted, the tissues forming a pseudoparenchyma which in mature specimens is hard and horny. Within the cortex is a loosely woven hyphal layer, the free surface of which constitutes the hymenium, and consists of basidia and paraphyses. These are arranged in an irregular palisade layer around a central cavity, which is usually filled with the spores. The basidia are tetrasporous, and the basidiospores are sessile, sterigmata being absent. During development the basidia and paraphyses become compressed, so that at maturity they appear as irregular angular tissues. The spores are binucleate, hyaline, and usually possess a thick epispore, enlosing granular contents. The peridium is at first filled with loosely woven hyphae; these later become gelatinized, when the peridiola lie embedded in a gelatinous matrix, the