生物演化过程中的突变性及其植物学证据

ON MUTATION OF SPECIES AND ITS BOTANICAL EVIDENCES

物种的形成过程并非遵循达尔文倡导的渐变论，而是当环境恶化时由祖先种通过自身的调节突然产生的。植物也可以因种间、属间或更高级分类单元间的杂交产生能繁育后代的新种，其过程无疑也是通过突变实现，对此本文暂不做深入讨论。在突变发生以后，生物的性状极少变化，为稳定期。古植物学中大叶系植物由无叶类演化到具大型羽状复叶的过程，有节类茎的纵脊在节上由直通到相错、叶由分叉到连合的过程；以及现代植物中的观音座莲从二次羽状复叶变为一次羽状复叶和车前草在南方种身上长出北方种的事实都证明了这一点。

Many paleontologists and biologists,influenced by Darwins “On the Origin of Species”,believe that evolution of species obeys “phyletic gradulism”.In fact,its a relatively sudden change from mother species to new species,and there are not any transitional characters between the corresponding characters of the ancestor and the descendant. This can be proved by the long term stability and short term change of the leaf morphology of the Pteridophyta and of the longitudinal ridge of the Arthrophyta in geological time,and also by the mutation of modern Angiopteris and Plantago.The reason which stimulates the species mutation is probably because of the suddenly change of the environment(the most important is the suddenly change of climate)and thus causes the gene in it to recombine.