False colour scanning electron micrograph (SEM) of pollen grains on the stigma (plant female sex organ), of annual meadow grass, Poa annua. The pitted outer wall of an anther (pollen containing) is in the background. Meadow grass pollen is a major cause of hay fever (medical term Allergic rhinitis & pollenosis). Sufferers produce an antibody, immunoglobin E (IgE), which attaches to cells in the nose & eyes. It reacts with inhaled pollen causing 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: X 185 at 35mm size. original is bw print B786/083