Melampsora pulcherrima

General: Aecial stage of this heteroecious rust occurring on stems, petioles, and leaves of annual mercury (Mercurialis annua) along riparian corridors under poplars (Populus), causing bright yellow to orange swellings and galls; the telial and uredinial stages develop on Populus.

Aecia: Crowded in dense, bright yellow to orange pustules with a whitish peridial border.

Peridial cells: Arranged in chains, thick-walled, 22-30 x 15-25 µm, walls 3-5 µm thick.

Aeciospores: Subspherical to slightly ovoid, 20.5-25 x 20-23 µm, hyaline wall 1.5-2 µm thick, surface densely verruculose.

Herbarium voucher: JTP1928/23.