当配子在融合之前从亲本体中排出到有水介质时发生体外受精，这是孢子植物的特征。
External fertilization occurs when gametes are expelled into a watery substrate from the parental bodies before fusion; it is typical of spore bearing plants.
例如在雌雄异株物种中的雌性植物和雄性植物，气生的和被水浸没的叶片，生活史中的配子体与孢子体的交替，叶肉和维管束鞘叶绿体等。
Examples include male and female plants in dioecious species aerial and submerged leaves alternation of gametophyte and sporophyte stages of a life cycle and mesophyll and bundle-sheath chloroplasts.
如果这种配子体能够产生可育的配子，那么形成的孢子体通常是四倍体，这样就可以得到大量的多倍体。
If such gametophytes produce fertile gametes, the resulting sporophyte is then tetraploid, and large polyploid series may subsequently be developed.
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