苔藓孢子的外壁纹饰不同，一般认为孢子外壁光滑是进化性状，外壁上各种突起排列密集的则较为原始。
Biyophyte spores have three types of aperture, the trilete is original one, the monolete is the evolutionary character and the katalept is mostly common one.
细胞学观察和扫描电镜结果表明， 突变体花药发育过程中， 花药中小孢子外壁异常、破裂， 最后没有花粉形成。
The mutant has small siliques with no seed set. Cytological observation showed that during anther development, the microspores ruptured and no pollen grains formed in the mutant anther locules.
当小孢子从四分体中释放出来，特殊类型的外壁已经形成。
An extine with its specific pattern had already been formed, when microspores were released from tetrads.
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