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In which class of gymnosperms fossils are absent ?
Cycadopsida
Coniferopsida
Gnetopsida
Both 1 and 2
Answers (1)
Classification of Gymnosperms -
Gymnosperms are divided into four groups:
1-Cycadopsida- Wood is manoxylic, Siphonogamous fertilization, male gametes are winged, they are commonly called cycads. E.g Cycas
2-Coniferopsida- commonly called conifers, e.g. Pinus. Wood is pycnoxylic, small ephemeral cones formed in groups, large and perennial female cones, siphonogamous fertilization, male gametes non-motile.
3-Ginkgopsida- represented by Ginkgo, also known as maidenhair tree. It is known as a living fossil. It is the only one living organism in this group, it has leathery and fan-shaped leaves, The veins are dichotomously branched, male gametes are motile and multiflagellate.
4-Gnetopsida- includes Gnetum, Ephedra, Welwitschia. Vessels are present in secondary xylem, orthotropous ovules with long tubular micropyle are present, resin canals absent.
-
Gnetopsida do not show fossilized plants. They have advanced gymnosperms.
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