Notes: Growing on the leaves of a ornamental rose (Rosa sp.)

Urediospores
Thin wall 1 – 2 µm, slightly roughened.
Spore range = (22) 24 – 27 (28) x (17) 19 – 22 µ
Average spore = 25.4 × 20.07 µ
Average Q = 1.28
15 urediospores measured.

Teliospores (Pedicels not measured)
Spore range = (65) 67 – 83 (88) x (31) 33 – 35 (36) µ
Average spore = 76.1 × 34.3 µ
Average Q = 2.22
10 teliospores measured.

I haven’t been able to key this convincingly in either “Phragmidium Species of North America” or “North American Rose Rusts”, I suspect I need something more recent…