Orbicule

Orbicules (syn. Ubisch bodies, con-peito grains) are small acellular structures of sporopollenin that might occur on the inner tangential and radial walls of tapetal cells. The ornamentation of the orbicule surface often resembles that of the pollen sexine. Different hypotheses about their function have been proposed, including them just being a by-product of pollen wall sporopollenin synthesis.