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THE AMERICAN NATURALIST [Vol. XLIII 



greatest detail, has acknowledged its improbability. 

 Bryophytes are no longer thought of as having given 

 rise to pteridophytes, but as illustrating here and there 

 the path along which the ancestral pteridophytes may 

 have traveled. Just how we should classify these an- 

 cestral pteridophytes makes no difference until we meet 

 them. 



The origin of gymnosperms is another conspicuous 

 illustration of {he same point of view. Paleobotany has 

 achieved no greater triumph than the discovery of an 

 extinct group of fern-like seed-plants, commonly called 

 pteridosperms, but better called Cycadofilicales. Our 

 knowledge of the group is remarkably complete, so that 

 their connections present no greater difficulties than do 

 those of living groups. Since most of these old seed- 

 plants had been described as paleozoic ferns, it was 

 assumed at first that this was a demonstration that 

 gymnosperms have been derived from ferns. Sober 

 second thought reminded us that ferns as we know them 

 are essentially modern; that the reputed ancient ferns 

 have turned out to be seed-plants; and that the actual 

 ancient ferns, therefore, are unknown. Conceding even 

 that some of the old fern-like plants are ferns, or Primo- 

 filices as they have been called, which is very reasonable, 

 the record of the fern-like seed-plants is just as old. The 

 ferns as we know them, therefore, probably did not give 

 rise to gymnosperms, but they may well illustrate stages 

 in the evolution of gymnosperms. 



The case is still clearer in connection with the origin 

 of angiosperms. When the Gnetales were first studied, 

 the logic of the morphology of that day suggested that 

 they had given rise to angiosperms, and so the connection 

 with gymnosperms seemed to be established. Nothing 

 could be more clear than that flower, embryo-sac, and even 

 vascular tissue were well on their way to the angiosperm 

 condition. But then Gnetales have no discoverable his- 

 tory, and angiosperms have, not to speak of other diffi- 

 culties. As a consequence, those who are most insistent 



