Trees

 

A tree can be defined as a large perennial woody plant. Though there is no set definition of minimum size, it is generally at least 6 m (20 ft) high at maturity, and with branches supported on a single main stem. Compared with most other forms of plants, trees are long-lived. A few species of trees grow to 100 m tall, and some can live for several millennia.

Trees occur in many diverse orders and families of plants, and thus show a wide variety of growth form, leaf types and shapes, bark, reproductive organs, etc. The earliest trees were tree ferns and horsetails, which grew in vast forests in the Carboniferous Period; tree ferns still survive, but the only surviving horsetails are not of tree form. Later, in the Triassic Period, conifers, ginkgos, cycads and other gymnosperms appeared, and subsequently flowering plants in the Cretaceous Period. Most species of trees today are flowering plants and conifers. The list below gives some examples of well known trees and how they are typically classified.
 

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tree-ho37.jpg (185502 Byte) winter-tree.jpg (95356 Byte) tree-yellow-flowers.jpg (378366 Byte) tree picture winter-snow-tree.jpg (104911 Byte)
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trees-59i7.jpg (153514 Byte) picture trees winter tree-1t0s.jpg (159306 Byte) picture tree tree-winter-fr6.jpg (218123 Byte) picture tree snow branch trees-spring-j3j6.jpg (333642 Byte) trees picture
tree-x7m2.jpg (130022 Byte) photo tree tree-a9k8.jpg (236062 Byte) tree-cvbg5.jpg (137596 Byte) picture tree winter-g5a1.jpg (136863 Byte) picture trees winter
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tree-road-rc2.jpg (142023 Byte) tree-vxk5.jpg (151401 Byte) tree-gce9.jpg (261427 Byte) tree-flowers-3jy.jpg (182409 Byte)
tree-uj63.jpg (105984 Byte) tree-d8es.jpg (143994 Byte) field-trees-n59.jpg (191019 Byte) hausen-albis-u3q.jpg (173849 Byte)
trees-ne9.jpg (224265 Byte) tree-7nm3.jpg (149787 Byte) tree-vtz5.jpg (170127 Byte) fir-trees-z4b1.jpg (296254 Byte)
tree-d0q5.jpg (103405 Byte) tree-picture-t5w.jpg (235753 Byte) tree-branch-zq7n.jpg (216801 Byte) tree-7nq6.jpg (196872 Byte)
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