False colour scanning electron micrograph of pollen grains of Timothy grass, Phelum pratense, also known as cat's-tail. A germinating pore is visible on one grain. A summer (June-August) grass pollen dispersed by the wind, it is a major cause of hay fever (Allergic rhinitis & pollenosis). Sufferers produce a sensitising 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 familiar symptoms of hay fever. Magnification: X214 at 35mm size. Original is bw print b786/136.