Sixty-two taxa are recognized in this study of the species of Puccinia completing their life cycle on Heliantheae. Six new species are described: Puccinia guatemalensis Parmelee on Zexmenia spp. and Wedelia spp., P. ghiesbreghtii Parmelee on Wedelia ghiesbreghtii, P. abramsii Parmelee on Geraea viscida (= Encelia viscida), P. chloracae Parmelee on Viguiera spp., P. calanticariae Parmelee on Viguiera spp., and P. praetermissa Parmelee on Lagascea spp. Six new varieties are recognized: Puccinia electrae var. robusta Parmelee and P. electrae var. depressiporosa Parmelee on Zexmenia brevifolia, P. caleae var. cuernavacae Parmelee on Calea spp., P. cognata var. echinulata Parmelee on Verbesina spp., P. cognata var. fraseri Parmelee on Viguiera fraseri, and P. affinis var. triporosa Parmelee on Viguiera spp. Three taxa have been restored from synonomy under P. abrupta, viz. P. subglobosa, P. ximenesiae, and P. affinis, the last two parasitic on Verbesina spp., the first on Rhysolepis (= Viguiera). P. tithoniae, P. nanomitra, and P. ordinata, are reduced to synonomy with P. enceliae var. enceliae, P. iostephanes, and P. melampodii respectively. New combinations include: P. enceliae var. aemulans (Syd.) Parmelee and P. abrupta var. partheniicola (Jacks.) Parmelee. A key based on uredinial and telial characters, others based initially on the hosts, and a host index are provided. Each taxon is illustrated by a photomicrograph from type material. Distribution and host extensions, supplementary to those given in Arthur's Manual of the Rusts, are indicated.

Fifty-six species, subspecies, and varieties of parasites are recorded from 23 locations, most from Isachsen in Ellef Ringnes I., Jacobsen-McGill Base in western Axel Heiberg I., and Hazen Camp in northern Ellesmere I. Previously published reports are assembled. Climatology and biogeography, as they relate to the fungi, are briefly discussed. Puccinia poae-nemoralis ssp. hyparctica Savile, Ustilentyloma pleuropogonis Savile (sp. et gen. nov., Ustilaginaceae), and Mycosphaerella oxyriae Savile are named. Clasterosporium caricinum and Columnophora rhytismatis are newly reported from the arctic.

Nine species of Gymnosporangium native to Eastern Canada and one commonly intercepted on imported nursery stock, but not known to be established, are described, illustrated, and discussed. Species occurring in adjacent United States but unknown in Eastern Canada are briefly mentioned. G. connersii sp. nov. and Roestelia brucensis sp. nov. are newly described on Juniperus horizontalis. R. brucensis is noteworthy because it has a repeating aecial stage and lacks telia. This is the first example of repeating aecia occurring in the genus. Aecial and telial keys are presented, emphasizing characters that permit identification in the field. One such character is the date of aecial maturity; it is suggested that this is a ready means of verifying apparent differences in morphology between taxa in this genus.

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