Bibulocystis gen. nov (Uredinales) on Daviesia (Fabaceae) and Albizia (Mimosaceae) in Australasia, with comments on the genera Cystomyces and Dicheirinia and rust genera with teliospore cysts

The five known genera of Uredinales with hygroscopic teliospore cysts, Cystomyces, Kernkampella, Ravenelia, Spumula and Uromycladium, are discussed. Of these, the monotypic Cystomyces, type species C. costaricensis, is the only one with teliospores composed of a simple, monohyphal pedicel attached to cysts, which bear the fertile cells. A rust of Daviesia species in south-eastern Australia was thought originally to be an undescribed species of Cystomyces. Type material of C. costaricensis has been studied. Whereas Cystomyces has teliospores borne on percurrently proliferating sporogenous cells and three, dark-walled fertile cells with apical germ slits, the Daviesia rust has teliospores borne on sympodially proliferating sporogenous cells and four, pale-walled fertile cells, each with an apical germ pore. Its teliospores show a complex arrangement of cysts and fertile cells, which is described and illustrated. These and other differences indicate that the Daviesia rust represents a previously unknown genus, described here as Bibulocystis gen. nov., type species B. pulcherrima var. pulcherrima. A single collection from the Central Tablelands of NSW with smaller, often irregular, teliospores is described as B. pulcherrima var. monticola. Only pycnia and telia are known for the two varieties. An emended description of the genus Cystomyces is given. The full-cycled rust of Albizia from New Caledonia described as Dicheirinia viennotii is compared with original material of the type species of Dicheirinia, D. binata. Whilst Dicheirinia has teliospores with ornamented fertile cells borne on sterile cells, teliospores of the Albizia rust have smooth fertile cells borne on hygroscopic cysts. As its teliospores closely resemble those of the Australian Daviesia rusts, it is transferred as Bibulocystis viennotii. The characteristics and taxonomic position of the other 11 species currently placed in Dicheirinia are summarised briefly. Bibulocystis is the sixth rust genus with hygroscopic teliospore cysts and the fourth recorded in Australia, with Kernkampella, Ravenelia and Uromycladium.