. Minnesota plant diseases. Plant diseases. Minnesota Plant Diseases. 25 forcibly eject their spores. Often by a change in the atmos- pheric conditions a large number of sacs burst at once and clouds of spores can be seen to ascend from the cup. The truf- fles have underground closed fruiting bodies which are related to the cups but never open except by decay of the w^alls. The morels and their allies have cups which are turned inside out, as it were, and are furthermore usually much wrinkled, and borne on stalks.~ Another very important phase of reproduc- tion in fungi lies in the kinds of sp
. Minnesota plant diseases. Plant diseases. Minnesota Plant Diseases. 25 forcibly eject their spores. Often by a change in the atmos- pheric conditions a large number of sacs burst at once and clouds of spores can be seen to ascend from the cup. The truf- fles have underground closed fruiting bodies which are related to the cups but never open except by decay of the w^alls. The morels and their allies have cups which are turned inside out, as it were, and are furthermore usually much wrinkled, and borne on stalks.~ Another very important phase of reproduc- tion in fungi lies in the kinds of spores produced by a given fungus. One and the same fungus may often produce more than one kind of spore. In fact, some fungi produce as many as five or six kinds. The wheat-rust, for example, forms one or more, — commonly two,—kinds of spores in the spring, another in summer and anoth- er in the autumn and when the autumn spores grow in early spring still another kind is produced. These spore forms fol- low in a certain way the seasons. The mil- dew, for instance, has summer spores and winter spores. In oth- er fungi the various forms may be called forth by differences in the substances upon which the fungus grows. In some fish-molds the production of the different spores can be exactly controlled by changing the food sub- stances. Sometimes a fungus which is or has been capable of producing several spore-forms continues under certain condi- tions to produce only one kind of spore. Our knowledge of such a fungus is incomplete until we know the other spore- forms which it is capable of producing. There is a vast num-. ^;^ Fi c. 11.—Kinds of spores produced by one rust fungus (a wheat rust) at different times. 1. Winter spore. 2. Basidiospore. 3. Cluster-cup spore. 4. Pycnidial spore (probably a function- less relic of a male sexual cell). 5. Summer spore. 1, 2, 4 and 5, after Ward; 3, after Ar- thur and Please note that these images are extracted from scanned page
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