http://en.wikipedia.org/wiki/Xylem [2]
https://www.boundless.com/biology/textbooks/boundless-biology-textbook/p... [3]
http://www.bbc.co.uk/schools/gcsebitesize/science/add_ocr_gateway/green_... [4]
http://www.biology4kids.com/files/plants_xylemphloem.html [5]
http://www.asknature.org/strategy/d7662735f5e44d5c879876f05652d091#.VKTP... [6]
Links
[1] https://hootsgo.org/?q=node/6344
[2] http://en.wikipedia.org/wiki/Xylem
[3] https://www.boundless.com/biology/textbooks/boundless-biology-textbook/plant-form-and-physiology-30/transport-of-water-and-solutes-in-plants-183/movement-of-water-and-minerals-in-the-xylem-698-11923/
[4] http://www.bbc.co.uk/schools/gcsebitesize/science/add_ocr_gateway/green_world/planttransportrev1.shtml
[5] http://www.biology4kids.com/files/plants_xylemphloem.html
[6] http://www.asknature.org/strategy/d7662735f5e44d5c879876f05652d091#.VKTP_SzDtXd