A fruit (bur) of great burdock, Arctium lappa (Lappa majus) attached to wool fibres. The picture shows a hooked bur entangled in individual fibres of a skein of wool. The hooks on the bur (green, terminating brown) have engaged with single strands of wool at the surface of the twisted fibre (blue). Visually, this attachment appears to be very tenuous, but in practice, though reversible, it is tenacious. Arctium is a member of the Compositae; the green hooks in the picture are the involucral bracts of the composite flower head. They serve to disperse the seeds within the fruit by attaching it to passing animals, including the clothing of humans. In 1955, the Swiss inventor George de Mestral was inconvenienced by burs when out hunting with his dog. He realised that nature had produced an ingenious reversible fastener. He went on to invent its modern nylon version, Velcro