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Unformatted text preview: rhizome or basal stem. Fronds "emerge" by circinnate vernation, a nearly unique uncoiling process. The uncoiled young fern fronds are called fiddleheads. Spores are produced in sporangia located in a sorus, which usually has a protective indusium. The indusium is a special layer of leaf tissue. The sori and their protective indusia (plural forms) vary in shape and are located on the underside of fertile fronds. Indusium location and shape is used in fern identification. Fern sori with Indusia Sori lacking an indusium...
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- Fall '09