MELAMPSORID1UM 



359 



spores roundish, 14 — 21x11 — 16/a, echinulate; epispore thinner 

 and smoother above. 



Uredospores. Sori hypophyllous, with yellow spots showing 

 on the upper side, collected in groups and mostly limited by 

 the veins, each sorus scarcely j\ mm. wide, surrounded by a 

 dome-shaped peridium which at length opens at the summit 

 (where its cells are drawn out into long sharp points, Fischer); 

 spores decidedly oblong or subclavate, orange, 22 — 40 x 8 — 12 /u,; 

 epispore colourless, with distant spines, often smooth above. 



Fig. 268. M. betulinum. Sorus of teleutospores. The fusion-nucleus 

 is seen in four of them, x 600. 



Teleutospores. Sori hypophyllous, always covered by the 

 epidermis, scarcely \ mm. wide, in dense clusters limited by 

 the veins, often spread over the whole leaf, reddish, then brown ; 

 spores prismatic, rounded at both ends, somewhat oblique, 

 30 — 50x7 — 15 fx\ epispore thin, scarcely thickened above, 

 nearly colourless, without perceptible germ-pore. 



iEcidia on leaves of Larix europaea, May ; uredo- and teleu- 

 tospores on Betula alba (both verrucosa and pubescens), August 

 — November, lasting through the winter on the decaying leaves. 

 (Figs. 267, 268; see also Fig. 37, p. 78.) 



It was Plowright who first, in 1890 (after many unsuccessful trials) 

 discovered that the Melampsora on Birch was connected with an secidium- 

 form on Larch (see Zeitschr. f. Pflanzenkr. i. 130; Gard. Chron. 1890, viii. 

 41). He performed the experiment in both directions, and his conclusions 

 were confirmed, eight years later, by Klebahn. The secidium in this case 

 does not belong to the caeoma-type, but to that of Peridermium (P. Laricis 

 Kleb.), having a peridium and resembling in its spores also Peridermium 

 Strobi. The forms on B. verrucosa and B. pubescens are, to a small extent, 



