6.请写一篇关于松树的英文介绍Pine trees (the genus Pinus) are distinguished from all other trees by: (a) having uncovered seeds borne in pairs on the bracts of (female) cones (as do other genera of the Pinaceae family) and (b) narrow leaves ("needles") arranged in bundles of 2 to 5 and with a permanent or deciduous sheath at their bases. Such bundles of needles are called fascicles (after the bundle of sticks around the axe which represented the power of the Roman senate). Pines are mostly large trees with a straight trunk with whorls of smaller lateral branches, but they have a wide range of habits varying from tall narrow trees to small bushy trees to prostrate shrubs. They are generally long-lived, usually over 100 years in suitable environments. The longest living individuals of any kind are the fabled intermountain bristlecone pine (Pinus longaeva) which currently has living trees at least 4,800 years old. (The root systems of the creosote bush (Larrea tridentata) may be even older). All pine species are evergreen, i.e., they keep their leaves for at least two growing seasons (and up to about 30 years in the case of P. longaeva) 。
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