Tapetal cells extend into locules surrounding many microspores during a stage of great vacuolation of microspore cytoplasm, expansion of sacci, and thickness increase of the exine.

• 此时气囊膨胀，花粉外壁亦加厚。关键词： 气囊小泡，胼脂质，花粉外壁内层， 外壁底层， 小孢子， 欧洲松， 气囊， 孢粉质接受粒，营养层，四分体，乌氏体。