DR KEITH WHEELER / SCIENCE PHOTO LIBRARY DR KEITH WHEELER / SCIENCE PHOTO LIBRARY
Female pine cone. Light micrograph of a longitudinal section through the female cone (strobilus) of a pine tree (Pinus sp.). The cone has a central axis (dark blue), from which emanate woody ovuliferous scale leaves (megasporophylls, dark purple to dark orange). At the base of each, on the upper side, are two sac-like megasporangia (thick purple walls) inside which is an elongated spherical ovule (dark red-purple). The ovule consists of outer integuments, inside which is the nucellus (megasporangium) which contains the megagametophyte containing two eggs (not seen). Magnification: x6 when printed 10 centimetres wide.
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