Phragmidium Species of North America: Differential Teliospore and Aecial Characters

Summary

1.	Segregation of the nineteen North American species of Phragmidium based on the character of the teliospore pedicel gives two sections, Earlea, including the six species whose pedicels are non-hygroscopic, and Euphragmidium, which includes the thirteen species with hygroscopic pedicels.
2.	The species are arranged according to three tribes of the host-family Rosaceae, six species occurring on Potentilleae, five on Rubeae, and eight on Roseae.
3.	The shape and size of the teliospores, the length and shape of the pedicels, the color and degree of marking of the wall, and the presence or absence of an apiculus are used as differential characters of the individual species within the sections Earlea and Euphragmidium on each of the three host tribes.
4.	On the basis of aeciospore marking the species are discussed under two types as follows: five species have aeciospores which are verrucose with irregular warts and twelve species have aeciospores which are verrucose with regular papillae. In addition one species has strongly echinulate aeciospores, and in one species aecia are unknown.
5.	The presence or absence of the aecial paraphyses and their characters are pointed out where characteristic of species.
6.	The value of aeciospore size, shape, and wall thickness in the determination of species is discussed and the advantage of using both aeciospore and teliospore characters is emphasized.
7.	The effect of different host species on teliospore morphology is shown in certain species.
8.	Keys to the North American species of Phragmidium, based on aecial characters and teliospore characters, are included.