Chaconia hennenii, a new holomorph species for Uredo maclurae and Uredo celtidis (Uredinales)

Chaconia hennenii is proposed as a new holomorph species for Uredo maclurae (= Physopella maclurae) on Maclura tinctoria (Moraceae) after the discovery of teliospores. Uredo celtidis described on Celtis (Ulmaceae) is synonymous with U. maclurae and belongs to the same holomorph species, as revealed by morphologically indistinguishable urediniospores and newly discovered teliospores. The host genus of U. celtidis is not Celtis, but most probably Maclura, too. Chaconia hennenii is unique among known Chaconia species by the apical wall thickening of the teliospores.