Several collections examined possess the delicate facies of an agaric which in Europe has been interpreted as B. titubans (Watling, 1982). Without more extensive field data, however, the majority of records cannot be substantiated. A collection from Piha Valley (1 iv 1974, legit J.C. Segedin, Segedin 1171) and one from above Huka Falls (on mown grass-straw, beside Waikato River, 27 x 1982, Taylor 1260) possessed the broader basidiospores associated with B. titubans. Taylor 190 (with grass, roadside bank, Holmes St., Oamaru, 26 iv 1964, legit L R Taylor) is immature but may represent the same taxon. in the Huka Falls collection some development of biporate spores was observed, something which was found to an even greater degree in Segedin 1161 (in grass outside entrance to Kauri Glen, Auckland, 28 iv 1974). Unfortunately the little field data available only indicates that the agaric is coloured much the same as members of the B. vitellinus group.

The large number of bi-porate basidiospores resemble those of many members of the strophariaceous gastromycetoid series; similar spores have been found in collections of Agrocybe from Kashmir and Poona, India (Watling & Abraham, in press). This fungus needs to be refound in New Zealand. In some ways the collection resembles Gastrocybe lateritia Watl. and G. incarnata (Peck) Baroni, although it is a typical agaric. This is yet another example of a bolbitiaceous fungus which reduces the hiatus between the true agarics and the so-called gastromycetes (secotioid). The Segedin collection lacks the colour typical of G. lateritia and G. incarnata but resembles the fungus named (ad interim) as Bolbitius rogersii (Heim, 1968); see Walling, Quadraccia & Tabares (ined).

The reader is referred to the discussion under B. vitellinus of which B. titubans has variously been considered a synonym, variety or subspecies (Watling & Gregory, 1981); Bell's record (1983) of B. vitellinus may refer here.

Pileus conical (15-30 mm), rapidly becoming plano-convex or plane (15-60 mm), with or without an umbo, bright yellow (yellow - chrome) darker at the disc, paler towards the margin where it becomes cinnamon-brown, shining, glutinous, finally fawn throughout except for yellow centre; margin striate, splitting and partially collapsing. Stipe 70-110 x 2-3 mm, tapering upwards, sometimes somewhat wider at the base, whitish or extremely pale yellow, pruinose or farinaceous throughout becoming white-silky, stuffed. Gills free or adnexed, pale yellowish with paler watery margin, becoming fawn, finally red-brown, fairly crowded, very thin and papery. Flesh very thin, distinction between pileus and stipe obvious, whitish or pale yellowish.

Basidiospores 11.5-14 x 7-8.5 µm, ellipsoid, thick-walled, sienna in water more strongly pigmented in aqueous alkali solutions, smooth; germ-pore large, central. Basidia 4-spored, a few 2-spored, clavate-pedicellate, 21-24 x 9.5-13 µm, hyaline, intermixed with sterile brachycystidia (pavement cells) 14-17.5 µm broad. Cheilocystidia irregularly lageniform with short or long and then flexuous neck, some simply vesiculose, 23-36(-48) x 9.5-12(-19) µm, hyaline; pleurocystidia infrequent, utriform or shortly lageniform,

23.5-28.5 x 7-10 µm. Pileipellis of spheropedunculate cells. Stipitipellis of hyaline, cylindric hyphae with clusters of irregular clavate, lageniform to vesiculose cells, especially at apex.

B vitellinus is widespread in temperate Europe and N America and along with B. titubans could well have been introduced into New Zealand with stock, feedstuffs or allied material; see Stevenson, 1982a and Bell. 1983. It grows naturally on a whole range of substrates and so could easily survive in a new area. The increased frequency of biporate basidiospores in collections of B. titubans and the appearance of 5-spored basidia in Taylor 246 may indicate some genetic in balance in certain New Zealand collections.

B vitellinus is a very variable fungus for which several varieties and subspecies have been recognised depending on size and growth pattern, although in many cases these are probably simply an expression of the food status of the substrate. After further field work Bolbitius sp. 1 (ZT 69/109), described below may be found to be included within the concept of this taxon. At present the persistently yellow stipe is significant.