. The British rust fungi (Uredinales) their biology and classification. Rust fungi -- Great Britain. MELAMPSORA 355 chains, ellipsoid to polygonal or subclavate, 18—28 x 10 epispore colourless, about 2 /x thick, rather densely verruculose, with no perceptible germ-pores; no para- physes. Teleutospores. Sori hypophyllous, subepidermal, small, roundish, red- dish-brown, then dark-brown; spores prismatic, more or less rounded above, pale-brown, 28—40 x 10—17 //,; epi- spore thickened (up to 3 p,) above. -18^;. Fig. 265. M. Hypericorum. a, teleutospores, under the epidermis; b, ascidiospore, witho
. The British rust fungi (Uredinales) their biology and classification. Rust fungi -- Great Britain. MELAMPSORA 355 chains, ellipsoid to polygonal or subclavate, 18—28 x 10 epispore colourless, about 2 /x thick, rather densely verruculose, with no perceptible germ-pores; no para- physes. Teleutospores. Sori hypophyllous, subepidermal, small, roundish, red- dish-brown, then dark-brown; spores prismatic, more or less rounded above, pale-brown, 28—40 x 10—17 //,; epi- spore thickened (up to 3 p,) above. -18^;. Fig. 265. M. Hypericorum. a, teleutospores, under the epidermis; b, ascidiospore, without paraphyses. On H. Androsaemum. On Hypericum Androsaemum, H. humifusum, H. perfora- tum, H. pulclirum. Not common. May—October. (Fig. 265.) What was described by Plowright as the uredo-stage of this fungus is stated by Fischer, Tranzschel, and others, to be the caeoma stage—the spores " being produced in short chains, with sterile intercalary cells, without paraphyses, but sometimes " (at least on Hypericum montanum) '• surrounded by a layer of swollen colourless cells which might almost be considered as an undeveloped ; Midler considers the form on H. montanum as a biological race, since he could not infect other species of Hypericum with spores from it. But Klebahn has proved (Zeitschr. f. Pflanzenkr. 1905, xv. 106) that a species of Hypericum can bear both the cseorna-forrn without paraphyses and the uredo-form with paraphyses. McAlpine (Rusts, p. 192) records that in Australia the uredo-sori have very abundant paraphyses, inter- mixed; he describes them as "hyaline, capitate, overtopping the spores, 50—68 x 18—24^; His species was on leaves and stems of H. japonicum,' and differs slightly from the British ones. His description of the uredo- sori is as follows : " Sori mostly hypophyllous, scattered or gregarious, at first bright-orange, becoming pale, pulverulent, up to \ mm. diam., erumpent and surrounded by the ru
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