Image from page 288 of “Journal of the Department of Agriculture, Union of South Africa” (1920)
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Identifier: journalofdepartm01sout
Title: Journal of the Department of Agriculture, Union of South Africa
Year: 1920 (1920s)
Authors: South Africa. Dept. of Agriculture
Subjects: Agriculture Agriculture — South Africa
Publisher: Pretoria, Govt. Print. and Stationery Off.
Contributing Library: The LuEsther T Mertz Library, the New York Botanical Garden
Digitizing Sponsor: The LuEsther T Mertz Library, the New York Botanical Garden
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or else only some of the shoots of thestool, the rest forming normal ears, though undersized ones. Thegeneral appearance of a typically diseased wheat plant reminds oneot a comnion cattle tulp plant, and it is from this similarity in appear-ance which has given rise to the South African name of fulp brand i ^^^^^lisease (Fig. 3). Fig. 4 is a photogi-aph taken in a wheat-fieldwhere the disease is prevalent, and shows in the foreground a normalstool on the right, and a diseased one on the left; the latter is less than FLA(i Smut of Wheat 255 half the height of the former, and has made no evident attempt toform ears. As a riile the plant is attacked so severely that it is unableto produce even young ears; sometimes a diseased stalk does form anear with grain, but usually the ear is attacked while still very youngand enclosed in its leaf sheath. Cause of Disease. Flag smut of wheat is caused by a fungus, Urocystis fritisi,Koern., and is ne;iily related to other -mut-causing fungi, such as
Text Appearing After Image:
Fi<;. U e.g., stinking smut of wheat or loose smut of oats. The only partsof the fungus which one can see without the aid of a microscope arethe spores or seed-like bodies of the fungus; these are black, and arereadily visible, but only because they are produced in such vastnumbers. Each spore itself measures only about one-thousandth ofan inch in diameter, so tin. t about a million spores pliaced side by sidein a single layer would cover an area of only one square inch. Fig.5 is a drawing of a single spore, magnified about 1800 times, showing •25 a Journal op the Dbpartmknt op Agriculture. how it is divided internally into a number of compartments or cells,two in this case, and surrounded by a jacket of smaller, lighter-coloured cells outside, which protects it from the effects of prolongeddiought. The spores are produced in the tissues of the leaves and arevisible internally as the black streak previously mentioned, and areliberated as a black, sooty powder. (See Fig. 2.) Infec
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