. Minnesota plant diseases. Plant diseases. Hi Minnesota Plant Diseases. story. Again, the sac spores may be of such seldom occur- rence that they have been entirely overlooked. Conspicuous examples of accessory spore-forms are seen in the green mold growths of cheese, in the powdery mildews or summer spores of the mildew fungi and in the honey-dew spores of the ergot. The groups of fungi discussed in this and the following chapter are subgroups of the sac fungi. (Figs. lo, 14 and below.) Yeasts and their allies (Saccharomycetes). Undoubtedly the simplest of all of the sac fungi, at least as f
. Minnesota plant diseases. Plant diseases. Hi Minnesota Plant Diseases. story. Again, the sac spores may be of such seldom occur- rence that they have been entirely overlooked. Conspicuous examples of accessory spore-forms are seen in the green mold growths of cheese, in the powdery mildews or summer spores of the mildew fungi and in the honey-dew spores of the ergot. The groups of fungi discussed in this and the following chapter are subgroups of the sac fungi. (Figs. lo, 14 and below.) Yeasts and their allies (Saccharomycetes). Undoubtedly the simplest of all of the sac fungi, at least as far as structure is concerned, are the yeast fungi, though this simplicity is to be explained by a reduction from a more complex form, due to peculiar habits. The yeast plant consists of a single sphere- Hke or somewhat elongated cell, so small in size that high powers of the microscope are necessary for their examina- tion. These cells multiply rapidly by bulging out little spherical "buds" which be- come separated from the par- ent cell and soon produce new buds in their turn. A cell may continue to bud off little plants as long as nutrient ma- terial is available. Sometimes the daughter cells do not sep- arate from the mother cells completely but remain more or less loosely attached and thus false filaments or threads are built up. Such are often found in the scums on the sur- face of yeast-containing fluids. The simple method of propa- gation by budding suffices the yeast plant for multiplication during favorable conditions and the ordinary yeast-plant-cell is often, moreover, capable of re- sisting successfully very unfavorable conditions. But when. Fig. 48.—Yeast fungus cells, a. Ordinary bread yeast, showing sprouting vegeta- tive cells. b. Spore formation in a yeast; four spores in a sac. Below are shown four free spores. Highly magni- fied. After Please note that these images are extracted from scanned page images that may have been digitally enhanced
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