Alternate title: pollen grain

pollen, flower: pollen and fertilization [Credit: Encyclopædia Britannica, Inc.] a mass of microspores in a seed plant appearing usually as a fine dust. Each pollen grain is a minute body, of varying shape and structure, formed in the anther, or male apparatus, in seed-bearing plants and transported by various means (wind, water, insects, etc.) to the pistil, or female structure, where fertilization occurs. The pollen grain of flowering plants (angiosperms) consists of three distinct parts. The central cytoplasmic part is the source of nuclei responsible for fertilization. The other parts constituting the wall of the grain are an inner layer, the intine, and an outer layer, the exine. The intine consists, at least in part, of cellulose. The outer and most durable layer, the exine, is very resistant to disintegration; treatment with intense heat, strong acids, or strong bases has little effect upon it. The composition of the exine is uncertain; its constituents have been termed ... (150 of 419 words)

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