65 Now examine the prepared slide of a mature pine ovule. It is drawn for you to the right. The megasporangium is enclosed in an extra covering called the integument . Together, these structures form the ovule . At one end of the integument is an opening termed the micropyle . It opens into a small ‘pollen chamber’. Inside the integument, the megasporangium wall is not as clearly evident. It is now referred to as the nucellus . The nucellus layer is most easily observed at the micropyle end of the ovule. The female gametophyt e develops inside the nucellus through multiple cell divisions. Archegonia are eventually produced at the micropylar end. Label the drawing and indicate whether each structure is haploid or diploid. After pollen grains reach the pollen chamber, they germinate and pollen tubes grow through the nucellus and into the archegonium. Fertilization is accomplished when the two non-motile sperm nuclei are discharged from the pollen tube into the egg cell. One fuses with the egg nucleus and one degenerates. The fertilized egg, or
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