Printhttp://en.wikipedia.org/wiki/Xylem
https://www.boundless.com/biology/textbooks/boundless-biology-textbook/p...
http://www.bbc.co.uk/schools/gcsebitesize/science/add_ocr_gateway/green_...
http://www.biology4kids.com/files/plants_xylemphloem.html
http://www.asknature.org/strategy/d7662735f5e44d5c879876f05652d091#.VKTP...
10th grade
11th grade
12th grade
