Two of the hosts are indigenous, A. novae-zelandiae var. pallida being endemic; A. ovina has been introduced from Australia. (Cheeseman, 1906, p. 131, 1073.)
The New Zealand form does not agree in all particulars with the European, differing mainly in the acuminate apex of the teleutospore. The cylindrical shape of the teleutospore, smooth, light-coloured wall, constrictions at the septa, and very long slender pedicels, separate this from other species found in New Zealand on Acaena. Specimens vary somewhat in the degree of roundness or otherwise of the apex, as well as in the length of the pedicels, for in certain sori the spores may all be rounded at the apex, and in others they all may be acuminate; the pedicels may average 100 mmm. in length, or may be twice this length. Generally, the larger the sorus the longer the pedicels.
Teleutospores are abundant in New Zealand, and in some collections literally cover the leaves of the host. As they may frequently be found on the same plant with Phr. subsimile, and occasionally even on the same leaf, the following method of separating the two on sorus characters may prove useful :-

Teleutosori compact, shining-black, usually small .....Phr. Poteztillae.
Teleutosori pulverulent, greyish-black, usually large ........ Phr. subsimile.

It is difficult to separate caeomata from uredosori, as they generally closely resemble one another; frequently sections are necessary to determine the difference. In this species, however, the uredosori are generally surrounded by the ruptured epidermis, which persists for a considerable time; this feature is generally absent from the caeomata, or, if not absent, is invariably less noticeable.

Hosts: Acaena Sanquisorbae Vahl. On leaves. Herb. Nos. 75, 765, 770. I. Karori (Wellington)., 100 m., G. H. C. 5 Mar., 1920. III. Routeburn Valley (Otago), 500 m, W. D. Reid ! 8 May, 1921. II, III. Table Bay, Wakatipu (Otago), 850 m., W. D. Reid ! 23 May, 1922. Acaena novae-zelandiae var. pallida T. Kirk. Herb. No. 296. II. Seashore, Seatoun (Wellington), E. H. Atkinson ! G. H. C. 27 Jan., 1921. Acaena ovina A. Cunn. Herb. No. 296. II. Seashore, Seatoun (Wellington), E. H. Atkinson ! G. H. C. 27 Jan., 1921.

0. Spermogones amphigenous, in small scattered groups, pallid yellow.
I. Caeomata amphigenous, solitary or crowded, often confluent, elliptical, less commonly orbicular, 0.5-1.5 mm. long, pulverulent, orange; encircled by a dense layer of cylindrical, hyaline, incurved paraphyses. m Spores subglobose or elliptical, 20-26 X 15-22 mmm.; epispore hyaline, finely and closely verrucose, 1-5-2 mmm. thick, cell-contents orange.
II. Uredosori hypophyllous, scattered, orbicular, 0.5-2 min. diam., pulverulent, orange, encircled by a layer of cylindrical or clavate hyaline, incurved paraphyses. Spores subglobose or obovate, 18-26 X 15-20 mmm.; epispore hyaline; finely and closely echinulate, 1-5 mmm. thick, cell-contents orange; germ-pores scattered, numerous, obscure.
III. Teleutosori amphigenous, chiefly hypophyllous, scattered or confluent, orbicular, 0.25-3 mm. diam., pulvinate, compact, shining-black, naked, with numerous spores in each sorus. Spores 1-5-celled, commonly 4, cylindrical, 55-95 X 18-25 mmm.; apex acuminate or rounded, not thickened nor papillate, base rounded; constricted at the septa; wall golden - brown, smooth, 2-4 mmm. thick; pedicel persistent, continuous with the spore, very long, up to 200 mmm. by 4-7 mmm. thick, hyaline, hollow, not or slightly swollen at the base, lower third closely"and finely verruculose; germ-pores 2-3 in each cell, conspicuous.

Distribution: Europe; Asia Minor; Siberia; Japan; North America; Australia.

Cunningham (1924a) referred this species to Phragmidium potentilla Karst; in 1930 he described it as an indigenous species occurring only on an indigenous host. It has been recorded only from Otago and is of no economic importance. This species will have to be renamed as the combination Phragoddhon acuminatum is already occupied.