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Pollen-tube growth and development of an embryo sac at the time of fertilization in Alnus.(A) Longitudinal section of mature ovule. (B) Pollen tube (arrow) in the mature ovule. (C) A diagram illustrating pollen tube growth in the mature ovary. The bold curved line shows the pollen tube. Arrowheads in B and C show the point where the pollen tube penetrated the funiculus. ch, chalaza; es, embryo sac; vs, vascular tissue. (Scale bar, 200 μmin A and 100 μmin B.)
