. Botany for agricultural students. Plants. YEASTS (SACCHAROMYCES) 377. Certain species^ give desirable flavors to some kinds of cheese and are quite usetul in tliis connection. Naked-ascus Fungi (Protodiscales). — Tiiis is a small group of parasites which attack seed plants. They produce no ascocarp and the asci are therefore borne exposed {Fig. 328). So far as known they have no sexual reproduction. They are regarded as simple Ascomycetes. One common species is the Exoascus deformans, which causes the disease known as Peach Curl. The mycelium develops in the tissues of the host and forms on
. Botany for agricultural students. Plants. YEASTS (SACCHAROMYCES) 377. Certain species^ give desirable flavors to some kinds of cheese and are quite usetul in tliis connection. Naked-ascus Fungi (Protodiscales). — Tiiis is a small group of parasites which attack seed plants. They produce no ascocarp and the asci are therefore borne exposed {Fig. 328). So far as known they have no sexual reproduction. They are regarded as simple Ascomycetes. One common species is the Exoascus deformans, which causes the disease known as Peach Curl. The mycelium develops in the tissues of the host and forms on the surface asci which appear as gray pow- dery films. One species attacks the young ovaries of Plums, causing the malformation known as " Bladder Plums," and one species causes Witches' Brooms on some of our deciduous trees. Yeasts (Saccharomyces). — The Yeasts are very simple Ascomycetes. In most Yeasts the hyphae are so short and simple that they appear as single globular cells The only reason for calling them Ascomycetes is that under certain conditions the cells form spores and then resemble asci {Fig. 329). On account of their ability to fer- ment sugars and produce carbon dioxide and alcohol, they are useful in making bread and in making alcohol, wine, beer, and other liquors which contain alcohol. When placed in dough they grow and work rapidly, and the carbon dioxide pro- duced causes the bread to rise. There are many kinds of Yeasts, and each kind gives a different flavor to the fermented product. For this reason brewers keep pure cultures of certain kinds of Yeasts, which give the liquor the desired characteristics. Their main method of reproduction is by the rapid division of cells, often called budding, in which small cells are apparently pinched off from the parent cell. The cells often remain in contact for some time after being budded off, forming chains of cells. Fig. 329. —Bread Yeast, Saccharomyces cerevisiae. a, single plant (X 600); b, a pla
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectplants, bookyear1919
