A leaf of the hybrid poplar, Populus x candicans 'Aurora'. The picture is a close-up view of the green and pale yellow areas that produce the variegated appearance of the foliage. Networks of lines show the vascular tissues that conduct water from the roots to the leaf (xylem) and sugars from the leaf to the roots (phloem). A major vein runs from centre top to centre right of the frame. Areas and islands of green comprise cells that have developed normal chlorophyll-containing plastids (chloroplasts). Areas of pale yellow are made up of cells where chlorophyll has failed to develop. This is due to random genetic changes within the cells. Each leaf has a different appearance. Pale green islands (top left) appear where white tissue overlays normal green tissue. Aurora poplar is an attractive columnar tree, but is unsuitable for small gardens due to its habit of spreading by suckers.