. The British rust fungi (Uredinales) their biology and classification. Rust fungi. ON GRAMINE^ 265 On leaves and culms of Hordeum vulgare and other species of Hordeum. Teleutospores, August, September. (Fig. 202.) The Dwarf Brown Rust of Barley, distinguished by the fact that it bears few two-celled teleutospores, but very numerous mesospores, which are variable and asymmetrical, slightly thickened at the apex (4—6/i), measuring 25—45 x 16 —24 fi. It is to be found in the uredo-stage all the year round. The teleutospores germinate in spring; Klebahn tried to infect, with their basidiospores,
. The British rust fungi (Uredinales) their biology and classification. Rust fungi. ON GRAMINE^ 265 On leaves and culms of Hordeum vulgare and other species of Hordeum. Teleutospores, August, September. (Fig. 202.) The Dwarf Brown Rust of Barley, distinguished by the fact that it bears few two-celled teleutospores, but very numerous mesospores, which are variable and asymmetrical, slightly thickened at the apex (4—6/i), measuring 25—45 x 16 —24 fi. It is to be found in the uredo-stage all the year round. The teleutospores germinate in spring; Klebahn tried to infect, with their basidiospores, the same forty-two ."peciea which he tested with P. triticina, but equally in P. simplex. Teleutospores. P. simplex may be worthy of being regarded as a distinct species ; it presents a little more difference from the other forms of P. dispersa than they do from one another. The sori of both kinds are amphigenous and more minute and punctiform (except on the culms), and the urodospores are of a brighter yellow. On Hordeum distichum I have found sori of P. simplex on the leaves, and with them those of P. graminis on the culms. It will be noticed that all the last five races are without any known secidium; it follows, apparently, that they must maintain themselves by their uredospores, but one might venture to suggest that future, unexpected, discoveries will throw light upon this obscure matter. Eriksson and Klebahn have both proved, by numerous infection experiments, that these races or subspecies of P. dispersa are all biologically distinct; with few, and doubtful, exceptions none of them can be transferred from its own to the other hosts. There are other forms of Brown Rust of which little is known. The secidium on Echium vulgare mentioned by Plow- right (Ured. p. 168) may belong to one of these; this plant was one of the forty-two previously mentioned, tested by Klebahn. I have also some specimens of uredospores on Airaflexuosa and A. caespitosa sent by Mr
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