E-Flora BC: Electronic Atlas of the Flora of British Columbia

Summary:
Cumminsiella mirabilissima is included as an example of the Uredinales (rust fungi). The rust fungi all grow on vascular plants, and often have very narrow host ranges. They do not have basidium producing fruitbodies, because basidia are produced from overwintering spores. There are up to five different types of spores specialized for different parts of the life cycle, and often two separate hosts that are taxonomically unrelated to each other. C. mirabilissima is an "autoecious" rust [all stages on one host], with its stages on Mahonia species (Oregon grape). The description is derived from Silverside(1), accessed October 20, 2004.

C. mirabilissima is found in BC (Ginns) and presumably widely in the Pacific Northwest through the range of Mahonia.

Fruiting body:
Aeciospores produced in aecia form on conspicuous swellings on the undersides of leaves in May and June (shown in the first and second illustrations). Urediniospores and teliospores form in structures called uredinia and telia respectively (also called uredinial sori and telial sori). "Uredinia and telia form on the undersides of the leaves - especially on overwintered leaves early in the season but also on new leaves later in the year. In this author''s experience there is no clear distinction between uredinia and telia, although telia tend to be darker. The sori may consist predominantly of urediniospores but with a few teliospores present, of equal amounts of each, or predominantly of teliospores with urediniospores still present. Old infected leaves more readily develop black and red colours on the upper surface." Uredinia (also with teliospores) are shown in the third and fourth illustrations.

Microscopic:
Aecial spores have a portion of the wall characteristically yellow-pigmented (shown in the fifth illustration). Teliospores have "two, rounded, more or less equal cells, on a long pedicel", while urediniospores are "pear-shaped, thick-walled and minutely spiny": these are both shown in the sixth illustration.