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THE BRITISH SMUT FUNGI 83<br />

Tilletia caries (DC.) Tul. Wheat Bunt<br />

[Lycoperdon tritici Bjerkander, 1775.]<br />

Uredo caries de Candolle, Flor. franc, vi, p. 78, 1815.<br />

Tilletia caries (DC.) Tulasne, Ann. Sci. nat., Bot., Ser. 3, vii, p. 113, 1847.<br />

Tilletia tritici (Bjerk.) WolflF, 1874.<br />

{Fusisporium inosculans Berkeley, J. hort. Soc, ii, p. 114, 1847 is based on the<br />

secondary sporidia of T. caries.)<br />

Sori in the ovaries filling the grain with spores, partly hidden by the glumes,<br />

4-7 mm. long. Spore mass powdery, dark brown to black, foetid when crushed.<br />

Sterile cells (intermixed with spores) globose, hyaline,<br />

smooth or indistinctly reticulate, 12-17 /x diam. Spores<br />

globose to sub-globose, pale brown, reticulate (reticulations<br />

2-4 (mostly 2-5-3-5) /x wide, 0-5-1-0 /x deep), 14-20 fj.<br />

diam. (Fig. 11).<br />

On Wheat (Triticum) and Rye (Secale) causing Bunt KiQ. 11. Tilletia caries.<br />

July-Aug. England; less common in Scotland. Spores, x 500.<br />

Exsiccati: Cooke, Fungi Brit. Exsicc, i, 53; ii, 429; Vize, Micro. Fungi, 130.<br />

Bunt of rye, which has only been recorded twice in this country (Salop.,<br />

1917, Cambs., 1929, fide 'Moore, W. C, 1943, p. 10), was included in Tilletia<br />

separata Massee (1899) and is sometimes distinguished as T. secalis (Corda)<br />

Kiihn.<br />

Spore germination. Prevost (1807) first figured germination, showing promycelia<br />

with thin, terminal sporidia and the later formed allantoid sporidia.<br />

Berkeley (1847) discovered the fusion in pairs of the fihform sporidia and this<br />

was confirmed by Tulasne (1854), Fischer von Waldheim (1869), Kiihn (1858),<br />

Wolff (1874 a), Brefeld (1883, 1888), Plowright (1889), and others. The filiform<br />

sporidia, which arise as protuberances at the apex of the promycelium as soon<br />

as it reaches the air, are 8-12 in number, septate, and 80-100 ^i in length. The<br />

apex of the promycelium remains tuberculated after the sporidia have fallen<br />

(Fig. 10 e). The allantoid sporidia, which develop on short pointed sterigmata,<br />

from filiform sporidia or from mycelium (Fig. 10/) are forcibly discharged (see<br />

p. 23). In the related dwarf bunt (see p. 85) branched promyceUa are common<br />

and tlie terminal filiform sporidia arp verj? numerous as in species of Neovossia.<br />

Hulea (1947) made a detailed study of spore germination in some species of<br />

Tilletia on wheat in Rumania.<br />

Infection of the host occurs at the seedhng stage (Prevost, 1807; Kiihn, 1858).<br />

The progress of mycehum in the host has been described by Lang (1912) and<br />

Woolman (1930) (see p. 13). Factors influencing infection are surveyed in<br />

detail by Holton & Heald (1941).<br />

Racial specialization. Infection of genera other than Triticum. Aegilops cylindrica<br />

(Vavilov, .1918) and A. ventricosa (Gaiidineau, 1932; Reichert, 1931) have<br />

been infected experimentally by Tilletia caries. Twenty-one other species of<br />

Aegilops were immune from the races of bunt used by Reichert.<br />

Agropyron cristatum, A.pauciflorum, A. subsecundum, A. inerme, A. spicatum,<br />

A. trichophorum, Hordeum nodosum, and Sitanion jubatum were infected

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