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92 THE BRITISH SMUT FUNGI<br />
(Fig. 16). Sporidia on the host in spring and early summer as white patches on<br />
the stems, in autumn on the undersides of the leaves, pear-shaped or elliptical,<br />
7_l4x4-5ft(Fig. 15 6).<br />
On Trientalis europaea.<br />
May-Oct. Scotland.<br />
Exsiccati: Vize, Fungi Brit., 136; Phillips, Elvell. Brit., 50 (as A. trientalis).<br />
Spore germination. Woronin (1882) germinated fresh spores during September-<br />
October from plants subject to moist weather conditions.<br />
Attempts at other times of the year failed.<br />
Germinating spores were found on the leaves and<br />
stems and on material kept under a watch glass.<br />
As many as 20 promycelia originated in succession<br />
from one spore ball. The promycelium issued<br />
through a round hole in the exosporium. The<br />
length varied with conditions and the promyeelial<br />
branches developed better in Ught than in darkness.<br />
fusion one of the pair developed a sporidimn.<br />
Unpaired branches also formed sporidia and fusions sometimes occurred<br />
between sporidia which had fallen off (Fig. 15 a).<br />
Infection of the host. Woronin (1882) placed geriiiinating spores on young healthy<br />
shoots of Trientalis europaea, covered with a thiu layer of soil and left over the<br />
winter. In spring the shoots grew above the soil and carried sporidia of the smut.<br />
UBOCYSTIS Rabenhorst,<br />
Herb. Viv. Myc, ii. No. 393, 1856.<br />
Type: Urocystis occulta (Wallr.) E-abenh. on Secale cereale, Europe.<br />
Synonym: Polycystis Leveille, 1846.<br />
Sori usually in the leaves and stems. Spore mass usually powdery. Spore balls<br />
composed of one to several permanently united fertile spores-more or less completely<br />
surrounded by a cortex of colourless or tinted sterile cells. Spores<br />
generally dark in colour. Spore germination, see pp. 94-100.<br />
This genus was monographed by Liro (1922) as Tuburcinia but to avoid<br />
changes in the names of major plant pathogens conservation of Urocystis<br />
Rabenh. against Tuburcinia Fr. has been proposed (see Trans. Brit. mycol.Soc,<br />
xxiii, p. 214,1939, and Phytopathology, xxx, p. 453, 1940).<br />
Urocystis agtopyri (Preuss) Schroet. Stripe Smut of Wheat.<br />
Uredo agropyri Preuss in Sturm, Deutschl. Fhr., vi, p. 1, 1848.<br />
Urocystis agropyri (Preuss) Schroeter, Abh. Schles. Ges., naturw. Abth. 1869-72,<br />
p. 7, 1869.<br />
Urocystis tritici Kornieke, 1877, fide G. W. Fischer, 1943.<br />
Tvhurcinia agropyri (Preuss) Liro, 1922.<br />
Tuburcinia tritici (Komicke) Lire, 1922.<br />
Sori in the leaves as elongated blisters parallel with the veins, at first beneath<br />
the epidermis which ruptures to expose the spores, the leaves splitting into