. The British rust fungi (Uredinales) their biology and classification. Rust fungi. ON GRAMINE^ 279 30—45 X 16—22 fi; pedicels short, brownish, persistent; an occasional mesospore is (k eX? Fig. 211. P. Poarum. Teleutospores; a, uredospore on P. nemoralis; 1?, para- physes with same; c, mesospore; d, teleuto-sori on P, pratensis; e, typical teleuto-sori of Uromyces Poae, on the same. ^cidia on Tussilago Farfara, about May, June, and August, September, very common; uredo- and teleutospores on Poa annua, P. nemoralis, P. pratensis, P. trivialis, about July, August and October—December, c
. The British rust fungi (Uredinales) their biology and classification. Rust fungi. ON GRAMINE^ 279 30—45 X 16—22 fi; pedicels short, brownish, persistent; an occasional mesospore is (k eX? Fig. 211. P. Poarum. Teleutospores; a, uredospore on P. nemoralis; 1?, para- physes with same; c, mesospore; d, teleuto-sori on P, pratensis; e, typical teleuto-sori of Uromyces Poae, on the same. ^cidia on Tussilago Farfara, about May, June, and August, September, very common; uredo- and teleutospores on Poa annua, P. nemoralis, P. pratensis, P. trivialis, about July, August and October—December, common but easily overlooked unless searched for. (Fig. 211.) First stated by Nielsen, the connection of the two hosts was demon- strated by Plowright and Klebahn. This heteroecious Pucainia diflfers from all others in having two generations in one year. The earlier crop of Eecidia begins to appear in May, and is followed by the uredo- and teleutospores on the surrounding leaves of Foa; these germinate quickly and the second crop of secidia is produced about August, and the second generation of teleutospores may be found on Poa from October. The latter germinate in the following spring, but according to Lagerheim the uredospores also, in a favourable climate, can survive the winter. This is certainly true in Australia, where (though the Pucainia is an introduced one) the uredospores have been found the whole year round. In that coiintry the Coltsfoot does not exist, and the fungus is carried through the winter by the uredo-stage; in fact, according to McAlpine, it is most common in the winter there. Arthur and Carleton say that the fungus does the same as far north as Nebraska in North America, where the Coltsfoot is only a naturalised plant. Uredospores were found alive in every month of the year at Washington, In the Scottish Naturalist ('84, p. 270) this species is recorded for Poa fluitans, but there may possibly be some error in this statement. Plow- right says t
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