Selfing is inhibited by genetic self incompatibility and also by the fact that within a single flower the stigma is receptive before the anthesis are ready to shed pollen. 由于遗传上的自交不亲和性以及花中柱头只能在花粉准备撒粉以前接受花粉，因而防止了自交。
A cruel twist of mutation among the Theelin led to genetic incompatibility among their own kind, dooming the species to extinction. 残酷的基因突变导致在希林人中间出现遗传不亲和性，把这个种族推向了灭绝的边缘。
