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96 THE BRITISH SMUT FUNGI<br />
Spore germination. Spores germinate as soon as they are ripe at an optimum<br />
temperature of 13° to 22° C. (Walker & WeUman, 1926). Thaxter (1890) first<br />
observed germination. Anderson (1921) described fiow the promycelium remained<br />
short and hemispherical, while from it arose a whorl of branches which<br />
grew indefinitely to form myceUum. Older parts of the mycehum became empty,<br />
the protoplasm collecting in the growing tips. The cells tended to separate and<br />
detached fragments started new growth in culture. BHzzard (1926) confirmed<br />
these results. He described the promyceHum as a spherical vesicle about 6-10 /i<br />
diam. From it arose four to eight branches of variable length which continued<br />
growth and produced in 12 to 18 hours on onion decoction agar a dense weft of<br />
myceUum. Fusions were not observed and no sporidia developed. All cells of<br />
the hyphae developing from the promyceUum were uninucleate and remained so<br />
during the saprophytic life. Parasitic mycehum consisted at first of uninucleate<br />
cells but binucleate segments were seen in the young sorus, and before sporogenesis<br />
all the cells contained two nuclei.<br />
Infection of the host occurs through the cotyledon before the emergence of the<br />
first leaf at soil temperatures between 10° and 27° C. (Walker & Jones, 1921;<br />
Szembel, 1926). No resistant varieties of onion of commercial value are known<br />
but a fertile amphidiploid, obtained by crossing Allium cepa with the resistant<br />
species A. fistulosum, may be useful ,in breeding resistant types (Walker,<br />
Jones, & Clarke, 1944). The fungus survived in soil for 20 years (Moore, 1948).<br />
Urocystis colchici (Schlecht.) Rabenh.<br />
Caeoma colchici Schlechtendal, Linnaea, i, p. 241, 1826.<br />
Uredo colchici Link, Handbuch, iii, p. 435, 1883.<br />
Polycystis pompholygodes (Schlecht.) LeveUle, 1846 p.p.<br />
Polycystis colchici Tulasne, 1847.<br />
Urocystis colchici (Schlecht.) Rabenhorst, Fung. Eur., No. 396, 1861.<br />
Tuburcinia colchici (Schlecht.) Liro, 1922.<br />
Sori in the leaves as bhster-hke swellings parallel with the veins, 0-5-1-0 mm.<br />
wide, 2-10 or more mm. long, at first beneath the epidermis which later ruptures<br />
to expose the spores. Spore mass powdery, dark brown. Spore halls globose to<br />
irregular, 14-34 x 14-22 ju., each composed of one or two (rarely three or four)<br />
spores surrounded by a layer of yellowish, ovoid, sterile cells, 7-10 /x diam.<br />
Spores globose or angled to somewhat elongated, flattened on side of contact,<br />
reddish-brown, smooth, 12-16 /u. diam.<br />
On Colchicum autumnale. Also recorded on imported bulbs of Colchicum sp.<br />
and Bulbocodium vernum {Bull. Minist. Agric, Land., 79, p. 109, 1934).<br />
June. Wilts. Uncommon.<br />
Exsiccati: Berkeley, Brit. Fungi, 309 [as Uredo colchici^<br />
Spore germination. Unknown.<br />
Urocystis eranthidis (Passerini) Ainsworth & Sampson, comb. nov.<br />
Polycystis anemones var. eranthidiaVa.&serixxi, Erb. Critt. Ital., Ser. 2, No. 549,1871.<br />
Urocystis pompholygodes var. eranthidis (Pass.) Passerini, 1877.<br />
Tuburcinia eranthidis (Pass.) Liro, 1922 [as 'T. eranthis'].