34.5 MB (6.4 MB compressed)
4252 x 2835 pixels
36.1 x 23.9 cm ⏐ 14.2 x 9.4 in (300dpi)
HERVE CONGE, ISM / SCIENCE PHOTO LIBRARY HERVE CONGE, ISM / SCIENCE PHOTO LIBRARY
Pine tree ovule. Light micrograph of a section through a pine tree (Pinus sp.) female sporangium, or macrosporangium. At centre right is the ovule (green), which will develop into two eggs, the females gametes (sex cells). It is surrounded by integument (red), a protective layer of cells. The whole structure is known as a macrosporangium. The gap between the two sides of the integument is the micropyle. During pollination male sex cells (pollen grains) enter through the micropyle. Pine tree macrosporangia are found on each scale of a pine cone and can take 2 to 3 years to mature. Magnification: x200 when printed at 10 centimetres wide.
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