False-colour scanning electron micrograph (SEM) of pollen grains around a split-open (dehisced) anther of the common oak, Quercus robur. Oak trees flower in May/June & produce copious quantities of pollen, which is dispersed on the wind. Oak pollen is a major cause of hay fever (medical terms Allergic rhinitis & pollenosis). Sufferers produce an antibody, immunoglobin E (IgE), which attaches to cells in the nose & eyes. It reacts with inhaled pollen to cause the release of various chemicals, including histamine. Histamine causes the mucous membranes of the nose, eyes & throat to swell & become inflamed, bringing on the hay fever attack. Magnification: x20 at 35mm size. Original is bw print B786/086.