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[tuh-rid-uh-spurm, ter-i-doh-] /təˈrɪd əˌspɜrm, ˈtɛr ɪ doʊ-/
1900-05; < New Latin Pteridospermales the order; see pterido-, sperm1, -ales Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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British Dictionary definitions for pteridosperm


any extinct seed-producing fernlike plant of the group Pteridospermae Also called seed fern
Word Origin
C19: from Greek pteris a fern + -sperm
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Encyclopedia Article for pteridosperm

loose confederation of seed plants from the Carboniferous and Permian periods (about 360 to 250 million years ago). Some, such as Medullosa, grew as upright, unbranched woody trunks topped with a crown of large fernlike fronds; others, such as Callistophyton, were woody vines. All had fernlike foliage; however, they reproduced by seeds, with ovules and pollen organs attached to the fronds. Gamete-producing structures in the seeds were surrounded by a hard inner integument and a fleshy outer layer. These features have led some authorities to speculate that these seeds may have been dispersed by animals. Some seeds were large. (Pachytesta gigantea, a seed of Medullosa, grew up to 7 cm [2.7 inches] long.) Pollen organs of seed ferns were also large and complex and were commonly made up of many pollen sacs fused into a large structure. Some authorities suggest that these large structures and the large pollen grains they contained were evidence of pollination by animals

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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